If it's a problem with the Ravel Grand Piano VSTi virtual instrument, which should be VST3, then you might try if with a new song or perhaps by enabling it manually so it's not blocked. Other than that, perhaps a previous version of the Ravel Grand Piano VSTi virtual instrument will work?
Another possibility if it loads is that there is too much stuff in the song.
Contrary to what some folks suggest, there are practical limits to what Studio One can handle without becoming overwhelmed.
I do everything on the Mac; so my experience is specific to macOS, and at present I am using an Apple iMac (Retina 5K, 27-inch, 2019) with 3.6 GHz 8-Core Intel Core i9, Radeon Pro 580X 8 GB, 64 GB 2667 MHz DDR4, and 4TB internal hard drive, running macOS Sonoma 14.7.2.
This might appear to make little sense, because it's a six-year old iMac; but (a) it's an Intel processor, and (b) it's quite peppy. Mostly the attraction is the price and it's being Intel-based, plus it has a 4TB internal hard drive (7200 RPM), where for reference this computer costs approximately $1,000 at MacSales, and then add $75 for the extended two-year warranty from OWC (MacSales parent), where if there is a problem, then OWC fixes it or replaces it with the same or better model. OWC refurbishes and certifies the used Macs, so having the OWC extended warranty is logical, and they actually honor the warranty in the same way that having an AppleCare warranty is logical and is honored by Apple without making you jump through hoops or beg to get a problem fixed..
It's compatible with all current digital music production software, including MODO DRUM (IK Multimedia), which for some unknown and quite illogical reason requires AVX Instructions (Intel) support.
The reasons for the 4TB internal hard drive are (a) having a vast festival of VSTi virtual instruments and sampled-sound libraries, including EW Composer Cloud+, IK Multimedia, Sonic Pass (UVI), Creative Access (Waves), All Access (McDSP), Reason+ (Reason Studios), 360+ (Native Instruments), and so forth, (b) not wanting to use external storage, and (c) not wanting to use SSD storage, which excludes (b) in a practical way.
Additionally, I want to avoid the new Apple silicon processors, which at present are not supported universally.
With this in mind, after doing quite a few experiments, I have developed the strategy in Studio One where I have 25 Instrument Tracks at any given time; and when I am happy with the current set of VSTi virtual instruments, I record them to corresponding Audio Tracks and then retire the Instrument Tracks or reuse the set of 25 Instrument Tracks for new VSTi virtual instruments.
I keep a handful of Instrument Tracks devoted to things like bass, kick drums, snare drums, and perhaps a few electric guitars, since those are the instruments I usually modify when mixing as a song develops; but generally there are more Audio Tracks and Bus Tracks, which as a rule have fewer processing and memory requirements, hence are handled efficiently by Studio One and are not limited by the processing and memory requirements of VSTi virtual instrument engines like Kontakt (Native Instruments) and so forth.
Putting this into perspective, when the sample rate is standard CD quality (44,100 samples per second)--which is completely sufficient for reproducing audio precisely and exactly at standard human hearing--each Studio One ".song' is processing 44,100 samples per second for each track ((Instrument, Audio, Bus), which for example if there are 50 tracks maps to over two million samples per second, which Studio One can handle but nevertheless is a lot of work--noting these are not samples from a sampled-sound library but digital samples (a.k.a., "lollipops"), which are different.
The digital samples contain all the information for all the instruments and voices, whether (a) it's a single guitar and one voice or (b) it's a 120-instrument symphonic orchestra and a 120-voice choir. At standard CD quality (44,100 digital samples per second), this causes the system and loudspeakers to reproduce the music exactly, and if you have a studio monitor system with a removable grill cover, you can feel the vibrations of the woofer to get a tactile sense of what the digital samples tell the computer, amplifier, and studio monitors what to do.
There are a few heavy VSTi virtual instruments that are what I call "processor and memory hogs", and if I need to use one of them, then I reduce the overall number of Instrument Tracks until I record the generated audio to an Audio Track and retire the heavy VSTi virtual instrument on its Instrument Track.
This strategy works nicely; and I do it in steps, where each step is archived, so if necessary I can revisit an earlier step by importing from a saved version of the Studio One ".song" and it's respective Instrument Tracks--including effects--when it's useful to revisit earlier steps.
SUGGESTION
You can do a simple experiment to determine whether "UADx Ravel Grand Piano" is a processor and memory hog.
Make a copy of your Studio One project via "Save As . . . "; and then delete all the Instrument Tracks except the one for "UADx Ravel Grand Piano" and perhaps a handful of tracks for basic drums, bass, and whatever else you need to put things into perspective (where the verses, choruses, bridges, and interludes start and end).
If "UADx Ravel Grand Piano" works nicely when there are fewer Instrument Tracks, this this provides a workable clue.
Let us know if this solves the problem . . .
For reference, there is another reason for limiting the number of Instrument Tracks, which is the fact that no matter how large your display happens to be, (a) you cannot see more than perhaps 25 tracks at a time and (b) actually you only can see clearly and distinctly the space of a standard note card at any time (approximately 3" by 5" or less), which is the reason note card apps default to a small size (TextEdit in macOS and Notepad in Windows).
I'm using the current versions of UA Connect (1.8.2.3451) and Ravel (1.4.16); and for the experiment I ran it as a VST3 rather than AU (which is Apple-only).
It works nicely on the Mac!
