Yeah I am not necessarily replace your phone - but if you try on another device (tablet) or other phone, you can rule-out your phone as being the problem. I am not familiar with your situation but I use the app on my phone without problem, I suspect 1000's if not millions of people use it so the app work, mostly.
You can go back an try your phone a dozen times but if nothing changes you really should expect different results.
You could apply for a visa now. Come into Thailand on a visa exempt, stay 30 days, fly to Malaysia for the week. When you return your visa should be ready, that's almost 6 weeks from now.
Twice they pulled me aside. One at the airport and once at the Nong Kai border crossing. Both times they said "next time you come back...". They did not tell me "never come back", "you can not come in". I have an extensive questionable visa history and they still let me in.
I wouldn't stress it. If you have round trip tickets they'll likely let you in. They will likely not even talk to you, just stamp you in.
You said "we", if I were in your situation I was travel like normal, except when doing immigration. I send my travel companion through a different line, that way if one of you gets denied entry, the other can proceed, and its not a total loss.
But if you qualify and if it's not a financial strain, why not get the visa?
Pay some high school kid to figure it out for you. I just finished my eVisa (Thai Embassy USA), it's a pain but it's a lot easier than going to the the embassy. If you do not have the computer skills (which is understandable) hire a kid who does have the necessary skills. Honestly, about the only difficult thing was making sure I had the correct file types.