The only real impact of modifying your service account username or password is that you'll have to retype all your stored credentials. I'd start with this first as it has little impact either way.
Try resetting the password for the ewdgssvc account you have set, and then see if the service will start. Here's a KB on how to do that. SolarWinds Knowledge Base :: Changing the account or password used for the Patch Manager service
If that doesn't work we can enable logging to isolate the specific issue that is occurring.
1. On the Patch Manager server open regedit and navigate to HKEY_LOCAL_MACHINE\SOFTWARE\EminentWare\Logging
2. Modify the value for Enable to 1.
3. Modify the value for Level to 3.
4 Try to start the service and wait for it to fail.
5. Once it fails go ahead and paste in the resulting datagrid logs. These will be in the Patch Manager Server directory (C:\Program Files\SolarWinds\Patch Manager\Server) and looks something like EminentWare.DataGridService.exe.43265.1328.0001.log.
Thank you so much. This worked!