Excellent plugin, support not great

I have been using this plugin for a couple of years and it has been great. However, about 3 weeks ago, my users stopped receiving emails. They are sent just fine, but only a handful of users are receiving them. My click rate was at around 75%…now it’s 5% or less. I have reached out for help as have 5 or 6 others who also started having this problem about 3 weeks ago. Not a single request for help has been addressed for those of us requesting it for this problem. It is unacceptable for such a common problem to go completely unaddressed for so long.