Connection help

I’m upset. I had 2 Ring doorbells before, version 1 & 2. Bought at different times.Then I got a 5G mifi, Inseego dual band(2.4/5) 5G Mifi as an upgrade hotspot… The doorbells stopped working. I learned the doorbells I had did not support dual band. I needed Ring doorbell 3 $190!strong text So I ordered one on ebay for $140. But it wouldn’t connect so I returned it. Then I ordered another from Amazon. But that won’t connect either. I’d rather not return this one too. Ideas?

Oops. Wrong forum.Can mod move it please?

I forgot to mention 5 other devices are connected to the mifi so I know it works.