Mail rules not working on macOs big sur 11.6.4

HI, I cannot get mail rules to run on MacOs Big Sur 11.6.4.

I have tried creating a new rule and then clicking on 'apply'., absolutely nothing happens.

I have rebooted then tried amending an existing rue and clicking 'apply', again nothing happens.

Over the years, I have created dozens of rules to auto-file, delete etc based on the sending e-mail address and date sent but nothing now appears to be functioning.

I don't know of any way to 'force' rules action without changing / creating a rule. Can anyone please help ?

Thanks in anticipation