Notes not syncing across devices #2

Notes 4.2 (555.10.42) under 10.11.6 hasn't updated any notes to match iCloud (as seen from iPhone SE on 11.2.6 and iPad Pro 9.7 on 11.2.5) since "upgrading" notes.

Even more bizarre: my iphone and ipad sync notes under [common account name] but Mini (Late 2009) and icloud.com/#notes2 are the same. Like there are two (count 'em, 2) [common account name] accounts that don't intersect.

And when I went to iPad - settings - Accounts & Passwords - [common account name] the **** thing spontaneously removed Notes as a thing (line item) that could be turned on, while I watched, and the account entry (and all the notes) just disappeared from my iPad - Notes. Took phone off WiFi and immediately emailed them to [common account name].

What did "upgrading" notes really do and how do I get around it and reconnect? iPad -> Settings now has a new "Notes" entry but "Accounts" -> Default Account doesn't list the [common account name] as an option.

Signing out of accounts (Mini or iPad) or restarting or updating iPad to 11.2.6 has had no effect. This was making my life easier for a couple years, now seems server-side "jest broked."