If you are NOT using the FreePBX End Point Manager, uninstall it. Your error points out the conflict. you cannot install both together as it causes bad juju, you need to install one or the other, not both.
I didn’t recently install the commercial EPM, so it seems like maybe they’ve both been installed and only in the last week something caused the OSS EPM to be disabled.
Problem fixed, thank you for the prompt, effective help!
In the process of trying to resolve this I uninstalled the OSS EPM in Module Admin. I was not aware that this would result in the loss of all the phone configs (or at least the OSS EPM’s link to them), which it did.
Since I have to rebuild all 40+ configs now, it seems like we might as well switch to the commercial EPM. If there are any caveats associated with doing that in an environment where the OSS EPM has been used, a link or info would be much appreciated.