[Help] Cannot change Minecraft Java version

I am running a server with friends, and each new snapshot that gets released - we all have to update our version

Today I went into my instance folder, and I cannot update 26.1-Pre1 -> Pre2

The "Change version" is greyed out

Anyone know why? and if possible can an update be pushed to tell people why change version is greyed out?

https://i.imgur.com/xndr3Qa.png