Thanks, but in my case that didn't work. Same error message still.
Same here, can't update filters anymore. Nothing works except uninstalling and re-installing Adguard.
I use the following filters (14/59):
English
Spyware
Social media
German
Mobile ads
Safari
EasyList
EasyList Germany
Easy Privacy
Fanboy's annoyances
Fanboy's enhanced tracking
Peter Lowe's list
Prebake
Anti-Adblock killer
21750 filter rules are used. This happens on both iPad and iPhone.