Hi Christos,
I found another post that may be helpful. I wrote the info below for your quick reference:
'“no access” is an issue with the authorization of Nuki Web on the device.
This normally happens if the access rights of the Nuki Web authorization have been restricted.
In your screenshot, I can see the app user as “Nuki Web ()” whereas, normally it is represented as “Nuki Web”.
Did you update, modify or delete the app user Nuki Web?
The only way to resolve this is to renew the authorization by deleting from Nuki Web and connecting via the app again, which you are currently doing.
Let me know if you are modifying the Nuki Web user created by the app. If not, please DM your Smart Lock ID (do not share it here) so that we can check the users in the database. Thanks.