I don't have any answers, but just wanted to chime in that I no longer get invites. I wonder if the process has changed? Do you have the availability badge turned on? It costs connects, so I have mine turned off.
I got several invites within a few days of eachother a few weeks ago. Good ones too. 1 of them turned into good ongoing work. I haven't gotten any since then. My guess is that they cycle freelancers around in the serach results so that everyone gets a chance.
Freelancers are cycled and now there are far too many freelancers using Upwork. This is what is causing your invites to decrease. You can try editing your profile to better fit the "algorithm" but even that is no guarantee. Unfortunately, this is going to keep getting worse without overall systemic changes imo.