I've got 4 email accounts setup on my Aquamail Pro (1.15.0-916) running on Android 8.0.0. Since the upgrade to Android 8.0.0 my Aquamail has stopped automatically synching my accounts. I've double checked the settings and everything appeared OK, and I can synch them all manually. Under each account where it advises on the last synch time it doesn't error out in red, it just displays last synch time.
Digging deeper into the settings I noticed a setting called Event Types, not sure if this is a new feature but was o ly set on 'System Auto Sync' , I added the Wi-Fi & Data option and its been working fine since.