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Can't connect to DB anymore, Debian, Robo 3T, PuTTY

Hello,
I can’t connect to MongoDB through PuTTY anymore. It worked before I started to practise backing up and restoring DB. The settings are the same in PuTTY nothing has changed.
Where should I start looking for the problem?
My setup: Windows notebook with Robo 3T, PuTTY (portforwarding activated), Debians 10 (with MongoDB), The IP of Debian is 192.168.178.164. The IP of MongoDB 127.0.0.1:27017
Status of db is running https://i.imgur.com/l9T68qp.png
My dbs overview https://i.imgur.com/hjMd8PJ.png

If no db is “selected” should Robo 3T be able to connect to this db?

Thank you.