VST3 plugins shown as "Stale" in Ardour

Plugins like rnnoise, lsp-plugins and sfizz were working fine, but right now they’re all giving the same log message as shown below:


I’ll be focusing on sfizz here especially, since it seems like other plugins work fine in different forms like LADSPA, VST2, etc. (I don’t know much about these, I might be describing it wrongly.)

When I try launching a project with sfizz in it, I get this message:

sfizz (VST3)
Those plugins will be replaced with inactive stubs until the session is reloaded.
It is recommended that you install missing, re-scan updated plugins, and re-load the session.

I’ve tried the recommended actions and I don’t think they have helped.
I use the nix packages of these plugins by the way. They were working fine until now.