This error/message comes from the
spyder-terminal plugin:
Terminal server could not be located · Issue #336 · spyder-ide/spyder-terminal (github.com) If you are using Spyder from the installers and you don't use the
spyder-terminal plugin, I would suggest you to update to the latest Spyder release (starting from Spyder version 5.5.0 the installer doesn't come with the
spyder-terminal plugin so the error should not appear with it). Otherwise, you will need to uninstall the
spyder-terminal plugin and try to contribute with debugging info in the linked issue to find a fix.