"login successful... connection problem, giving up" after reboot

My:
i-0a962b3f00a12bb6c
Ubuntu c5.large instance had been running for 237 days without hitch, but the disk got full while I was trying to update something and despite deleting ~450Mb of data the program was still stuck with a disk write error, so I shut it down, waited for it to finish, then started it back up again.

Now when I try to connect via windows remote desktop like I always do, I put in my name and password and it shows:

connecting to sesman ip ...
sesman connect ok
sending login info to seesion manager, please wait...
login successful for display 10
started connecting
connection problem, giving up
some problem

Can anyone point me towards sorting this out? I "deleted" the ~450Mb, not moved them using [rm -rf] not just moved them to the trash bin, and looked in the trash bin to make sure all was well... Maybe something to do with the disk still thinking it's full though? Maybe to do with these e-mails?:
"We are writing to inform you that Canonical Group Limited has added a new version to Ubuntu 18.04 LTS - Bionic on AWS Marketplace. As an existing customer, your subscription to the product, any running instances and access to previous versions are unaffected. However, Canonical Group Limited does recommend you to update to the latest version, Ubuntu 18.04 LTS - Bionic/Ubuntu 18.04 20210623 by visiting"

Thank you.