Why does QB and bank accts keep disconnecting?

Checking the error code on your account tile is the fastest way to pin this down, since a full disconnect right after posting usually traces back to how the reconnection was set up rather than the posting action itself. Head to Accounting, then Bank transactions, and look at the account tile for an error code. If one shows up, click Fix now on that tile, and when you sign back in with your bank credentials, make sure to select all accounts you want QuickBooks to access.

It's also worth checking whether anyone else has access to this connection and might be reconnecting or updating bank credentials around the same time, since overlapping reconnections can cause the link to keep dropping.

Do you see a specific error code on your account tile, or does it just say 'disconnected'?  

Please let us know in the comments if the issue persists.