Yes, you will need to retest and fill out the USVI portal again. There is testing on Jost Van Dyke and you can arrange once you arrive. Your host on Jost (see what I did there) can help you with the current details. Your test must be taken 3 days in advance if you are flying and 5 days if you are ferrying back.

The 48 hour rule was changed a few weeks ago (see attached from 4 October).

Just to clarify, you don't need to fill out the BVI Gateway any longer. You fill out the health portal to pre-register for your arrival test here.