when I wanted to install MAAS with ansible-playbook I set the last version and subversion but that returned an error because It did not accept the version that I entered. can you help me for upgrade that to beta?
For the sake of testing you can just login into the region vm and run sudo snap refresh --channel=3.3/beta maas.
btw isn’t
maas_version="3.3"
maas_installation_type="snap"
maas_snap_channel="beta"
working?
I had trouble upgrading to the beta version. I deleted the rack and region virtual machines re-created them and reinstalled Maas with the beta version. I deliberately turned off the virtual machines and turned them on again (assuming that this problem happened in the production environment and I need to find a solution for it), but in the test phase, I encountered the 502 problem again.
can you upload /var/snap/maas/common/log/regiond.log somewhere like at pastebin.ubuntu.com?
log size was 50MB and the browser crashed when I copied logs to textarea.
I uploaded that to Mediafire as a txt file: file link
logs were pretty self explanatory 
django.db.utils.OperationalError: connection to server at "172.16.1.219", port 5432 failed: Connection refused
MAAS fails to connect to the postgres database that is supposed to be reachable at 172.16.1.219:5432
so what are next steps?
It seems to be a configuration issue. You have to make sure postgres is properly configured and listening at that address