Went back and forth a bit with jstefanop for a bit to figure out why my Apollo II could sync & solo mine, but wouldn't stay connected to a pool, wanted to share what we found in case others encounter the same issue:
Asus routers (and presumably others) have a feature called AiProtection with a a Two Way Intrusion Protection setting that will specifically block bitcoin mining.
https://kmpic.asus.com/images/2023/01/18/e13e2ea5-dbbf-4bb9-835d-b9adef8687f7.pnghttps://www.asus.com/support/faq/1008719/#a3You'll have to disable this if you plan on mining behind any router with a similar protection. Worth noting that it can sometimes be automatically re-enabled during a firmware update.
