A50+ does not turn on from the standard power supply

Hi guys!
Please forgive me for my English. This is not my native language.
My A50+ no longer turns on from the standard power supply. It used to turn on, but it doesn’t turn on anymore.
I Plugged A50+ in via USB to my computer and did a factory reset, but that did not solve the problem.
24V supply voltage is present on the adapter.
A similar problem was discussed here in Aprel-May, and it was solved by the new firmware. My device has a new firmware.
I tried to solve my problem in the ways described here, but the problem did not go away.
Could you help me?

Hi, You could measure the output voltage of the power adapter, and confirmed it’s fine, right?

And if the power is fine, could you try to plug the 24V, and also the USB cable which could supply the 5V to the system. And check if the device could drive the speaker for sound. If so, I’m afraid most likely the device DCDC power would be defected. And can’t be fixed by firmware.

Hello! The external power supply is ok. I connected it to another working A50 +, devices work fine. I connected the problematic A50+ via USB, it started up, then connected the external power supply, the speakers work fine. Disconnected USB, the device works normally from an external power supply. Turned off, connected after 10 seconds an external power supply, the device turned on. I turned it off, waited until the LED on the external power supply went out, connected it again, the device does not turn on.

Hello Frank. My problem is not solved, the device is under warranty. I bought it from AliExpress. How can I solve the problem? I live in Russia. Thank you!