TS-412 (QTS 4.3.3) no internet due to non-existent default gateway

I’m getting error messages that my TS-412 NAS (running QTS 4.3.3) has DNS issues and that I should alter the DNS and/or default gateway settings in Config > Network > TCP/IP. Problem is, that these options are blocked (greyed out): I can’t choose automatic DNS and the gateway shows a VPN connection that has been deleted long ago, but that can’t be changed anymore.
How should I fix this? Using the command line or by editing some config file?

Please help.
Thanks!

Are you using “admin” to do your changes?

Yes, I’m using an admin account

No…I mean the “admin” not just an admin

Sorry, I meant to say I’m using the “admin” account…

Hmm…ok

Have you tried a 3 second reset ?

I turned it off (shutdown from within QTS) and on again. No effect…

A 3 second reset is done via the pinhole in the back

Ahh… Did know that feature. It’s very important to keep my 12 TB of user data, but that should be unaffected, I think. I’ll have to backup all my network settings first, in order to being able to restore them manually after the reset. I’ll let you know if this helps.

Data should not be deleted … of course make sure you have full backups at all times

The 3-sec reset did the trick! The error is gone.
Thanx!!