LimeSDR mini - Problems with transmission

Unfortunately I haven’t received any comments yet.

I’ve been following some topics related to my problem, like this:

But I couldn’t find a solution to my problem.

I’ve been thinking, since I can receive signals like FM stations. At least the RX part is apparently OK and the software and configuration also OK.
Is there any additional test (besides from my test in gnuradio) that could you please suggest me.

Best regards,