Configuration seems OK to me.

Debugging Nonce::verifyNonce() I noticed:

1. self::getOrigin(); returns 'https://somedomain.org:443'
2. self::getAcceptableOrigins() returns array('http://somedomain.org', 'https://somedomain.org')

Thus, the returned origin is not found in the acceptable origins array.

Note the missing ports in the acceptable origins.

Matomo version 3.13.6.