I've built MegaDrum, programmed MCU's correctly, and I can see MegaDrum menu on LCD but I cannot get any MIDI activity. What is wrong?

I've built MegaDrum, programmed MCU's correctly, and I can see MegaDrum menu on LCD but I cannot get any MIDI activity. What is wrong?

Before trying to troubleshoot the problem, swear that all resistors
(measured with a tester), capacitors and an inductor of correct values
and you have no short circuits or breaks. After that tell about the problem on the forum and I'll try to help. I'll be frustrated if it will have turned out to be a short or a break after all.