Beta channel selection disabled and unselectable after reboot

[Fabio_Danzetta]

Hello everyone,
Yesterday I downloaded the iso of the latest 24h2 release preview and installed it, then chose the beta channel as the insider subscription type, but when I restarted it didn't keep the selection because I saw myself in release preview without the possibility of choosing the beta channel, which in fact is grayed out and not selectable, while dev and canary can be chosen.
Currently, I am in release preview with build 26100.1742 ge_release.
I installed all the updates and restarted again, but nothing has changed.
Can you tell me why and where I went wrong?
Thanks everyone.

[#2]

If you are in a Dev channel build (currently any build higher than the 22000.xxx range) and you cannot rollback to any build in that range or lower, you need to clean install a stable/Beta/Release Preview build to get out of it.

[#3]

@DanielRobinson the build i installed is from the release preview branch and not dev.
Can you please clarify this?
I am new to the insider program, thanks.