You’d need to check which of the relevance clauses are evaluating as ‘false’. You can copy them and run them individually on the relay using the fixlet Debugger.
The most likely cause for this in particular though, is that you need to upgrade the Root Server to a given version before the Relay upgrade for that version becomes relevant.
In fact that was the first I did, manually update the BigFix Server, after that, I update the relays also manually, but the clients, I want to update them with a task automatically, and that’s where It does not allow me, since the upgrade options are disabled.
Clients need to re-register to know if their parent is the right version to upgrade. That can take time but as this post was 12 days ago then you should have passed that time by now.
Also be aware that fixlets enforce the best practices. So if you are trying to install a 10.0 upgrade on a 9.5 relay or server it may not become relevant as well.