MMDVM_HS_DUAL don't work at Pi4 as USB device

[dl1bz]

I have a Pi4B/4GB. I flash the MMDVM_HS_DUAL correct for USB use - with a Pi3B+ all worked ok (I try both variants, with old and new bootloader).
If I use the same modem with a Pi4 - the modem disconnects after a few seconds. No /dev/ttyACM0 will be generated at any time.
I try the USB3 ports and the USB2 ports - no way to run. Btw, using as a HAT with GPIO all worked with Pi4.

73 Heiko, DL1BZ