second monitor "no signal" on mac mini m1

I just purchased a Mac mini m1 and set it up. Now, I formerly had a Mac mini 2014 with two monitors that were plugged in via a thunderbolt 2 - vga adapter.

After reading advice on the web, I purchased 1 usb-c - vga adapter and one hdmi - vga adapter.

The usb-c one works great, but while the computer "see" the second hdmi monitor on system preferences, I get a "no signal" display on the monitor.

Is there anything specific that I should have checked with the adapter? I don't want to buy new monitors since the ones I have work perfectly. But they only have vga or dvi connectivity.

Suggestions?