Incompatible runner after upgrade to 2021.1 (build 92597)

Hello,

I have 10 agents, running Windows.

After upgrading the server to 2021.1 (build 92597) all of my agents became "Incompatible runner" for:

NuGet Installer

but after disabling the step that requires Nuget, I get  "Incompatible runner" for the next step:

MSBuild

after disabling that step, I get  "Incompatible runner" for the next step:

Visual Studio (sln)

so I am getting "Incompatible runner" for any of the tools i am using in my build configurations.

but I have all of them installed either as a tool or as a plugin, under Server Administration.

and all of that have worked before the upgrade.

things i have tried so far:

1. created a custom zip tool to trigger a manual upgrade, as suggested in
https://youtrack.jetbrains.com/issue/TW-61690#focus=Comments-27-3666146.0-0

2.  tried adding teamcity.tools.loadingOnDemand.enabled=false to install all tools.
and i see all of the tools are installed under C:\buildAgent\tools on each agent.

3. reinstalled the agent (to a fresh directory using agentInstaller.exe)

but still getting "Incompatible runner" and can no longer build.

please help me resolve this issue.

thank you.