You need to be in US waters. On Friday, I tried submitting twice while in the vicinity of Nanny Cay and it was rejected, but once I got near Flanagan Island inside US waters the submittal was immediately accepted and moved to PENDING status for CBP review. Pretty sure it uses your GPS location to make this determination.

Please note that US Permanent Residents and non-US citizens will NOT be approved for entry to USVI from BVI (or other foreign country) using the ROAM App. They need to continue to present themselves for photo and fingerprints (as usual) at Cruz Bay or Charlotte Amalie C&I. Found this out on Friday. Good excuse to visit The Landings for a bushwacker.