'Validation unavailable, please use manual input.' after module update 1.8.2 > 1.9.0

[MikeD-J]

After filling in postcode and house number getting 'Validation unavailable, please use manual input.' instead of correct results (e.g. 'Unknown postcode + housenumber combination.' when filling in an imaginary combination).

After some debugging the problem became clear, with the module update the api.url went from https://api.postcode.nl to https://api.postcode.eu, though, this didn't get updated (automatically) in the database/config.

To fix temporary locally:
Go to core_config_data table where path = postcodenl_api/development_config/api_url and change https://api.postcode.nl to
https://api.postcode.eu.