There has been several issues that prevented evaluation, notably Evaluation error is blocking jobsets · Issue #83647 · NixOS/nixpkgs · GitHub.
The aarch64 builders were also timing out due to I/O starvation – that should be fixed now as well.
Hopefully, Hydra - Build 116168962 of job nixos:trunk-combined:tested or Hydra - Build 116295167 of job nixos:trunk-combined:tested will succeed now.