Agents not upgrading when upgrading from Version: 2021.05.15.0632 to latest

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**Describe the bug**
We are attempting to upgrade from the monolith Version: 2021.05.15.0632 to the latest docker version. I was able to get the database copied over, and with nginx redirects/overriding of methods - the agents to connect but show 'Outdated'. The agents aren't able to auto-upgrade. I also tried running 'update agents' from the server config page, and I see that they're trying to pull Remotely_Installer.exe to upgrade. The Remotely_Installer.exe no longer exists in the newest version so our logs show '404'. It seems like the newest version uses the Remotely.zip ( based off x86 or x64 )

Is there an alternative to the Remotely_Installer.exe that I can point my nginx proxy to so that the agents can auto-update? or is there a more creative approach so when they do connect to the newer install they can download the newest zip and update themselves?

I've also tried running a WinPS against them from the newest version, however that also must not be supported.

**Remotely Version**
Server (can be found on about page): latest
Agent (can be found in device card): Version: 2021.05.15.0632

**Expected Behavior**
The agents should auto update to the newest version

Begin with the server config page's “update agents” flow and the request for Remotely_Installer.exe; compare it with the x86/x64 Remotely.zip artifacts and the nginx redirects. Done means agents at version 2021.05.15.0632 can upgrade to the latest Docker deployment, with the WinPS attempt also checked for compatibility.

Written by the indexing model from the issue text.