Browser extensions are a dead end for Twitter DMs now. They've tightened detection massively in the last few months.
VM + proxy + extension = detected instantly. The extension signatures are flagged, plus VM fingerprinting is trivial for them to catch.
You need proper emulation or mobile automation. Desktop browser automation for DMs is basically over, even with premium accounts. The platform can tell the difference between human mouse movements and programmatic clicks.
Try mobile emulation tools or hire VAs to do it manually. Way more expensive but actually works.
Thing is even with that most DMs are ending up in the hidden request cause people disable them.
Best is letting comments on the last posts.