Line Charts with 120 sec. entries won't work

Hello there,
Iโ€™m new here but I thought you might help me.
I have a dataset with multiple dates per day. Data is recorded every 120 sec. I have two columns in the original csv for the time. Date and Time. So I converted date to datetime and time to timedelta. The result from addition these two seems good. But I canโ€™t plot the values per date_time. The time axis seems not to recognize the time.
Iโ€™ll add pictures in the topic.

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Could I do something better to describe the Problem?