EGroupware serves “only” as an editor for the sieve scripts on the mail server. This shows what is in the sieve scripts on the server.
If you can access the scripts, you should check them. If it supposedly works and if it just doesn’t seem to be displayed anymore.
Do you perhaps change the sieve-scripts on the mail server in another way?
Should the scripts still be there: are the file permissions correct?
Is this a mailbox that multiple users have access to?
Of course you can also turn vacation notice on and off automaticly by date. But this is another, longer story. One for our Support.