503 in frontend when base url configured for the site has a path

[Stig Nørgaard Færch]

Base:
https://example.com/somepath/

Error mesage:
Exception handler (WEB: FE): Error, code #0, file ***/public/typo3conf/ext/nnrestapi/Classes/Middleware/PageResolver.php, line 96: Call to a member function setRequest() on bool

Request_url example:
https://example.com/somepath/api/facebook-sharing/connection-status

Observed that if I’m logged into the backend with the domain, the endpoint now works. When I logout again, the error is back.

[Stig Nørgaard Færch]

This issue can be closed. The reason was a misconfiguration on my part.
I include the TypoScript using ExtensionManagementUtility::addTypoScriptSetup, but included it in ext_tables.php, where I should have been using ext_localconf.php, as ext_tables.php is only executed in backend context.