Suspended GMB causing loss in SERP'S rankings?

Hey guys, a local Licensed and Insured plumber had been doing fine in google SERP's rankings for years now but got his local business account suspended last month and doesn't know why. Thing is like few weeks after the suspension he is now losing his regular Serp's rankings.

I had always thought the GMB [3-pack] was independent of the Serp's so I am not understanding why he is losing his Serp's rankings, can anyone explain why please and also what he might do to get back the Serp's...

Suspended GMB causing loss in SERP'S rankings? WordPress ...