Just in case, go to iOS Settings App → Safari → General → Content Blockers and check that all six AdGuard content blockers are switched on (this is important because they are intertwined and need each other to work properly).
Open AdGuard → Settings → Safari protection. The toggle should be on (it shows on the main screen as well).
Go to AdGuard's main screen and tap (Update Filters) in the right upper corner. Check if your problem is solved. If not, proceed to the next step.
Check which filters are enabled, if any: Settings → Safari protection → Filters. Our recommended list that should cover most of ads is as follows:
AdGuard Base filter
AdGuard Mobile filter
AdGuard Tracking Protection filter
AdGuard language-specific filter (for languages of websites that you view in the web)
If you don't want to see cookies, third-party widgets, "Like" buttons and such, enable these too:
AdGuard Annoyances filter
AdGuard Social Media filter
If it doesn't help, please let us know: Settings → Support → Report incorrect blocking.