Unfortunately, Minecraft: Bedrock has decided not to accept normal numbers in the startup parameters and they want for a longer string instead.
Here's an example of how you probably tried to change the server version:
This is right, but it wont work. Bedrock will ask for "x.x.x.x" <-- 4 dots. This version can usually be found in the Minecraft Wiki, and in this case the version would be "1.20.7201.0". It wont always be 01.0 added to it, it'll be random sometimes.
Once you have found the correct numeric version, go ahead and reinstall the server (will delete previous data) for the new files and version to be generated.
