Ty, I read about that but I try to keep my apps as default as possible in an attempt to conserve battery life.
Anyway, I ended up treating the ad blocker nag like another ad and following, How do I determine what domain an ad is coming from?, to determine it was coming from getadmiral.com. I added that to the blacklist and it appears to have solved my issue. No more nag!
Edit: The nag returned so I searched further for PiHole and getadmiral and found this topic, https://www.reddit.com/r/pihole/comments/90k2jw/piehole_use_detection_by_levin_labs_getadmiralcom/ ... turns out getadmiral is blocked by https://firebog.net/ tick lists. I'm going to give that a shot.