Aha, I suspect you are using some sort of Windows server ? In this case probably you have run into the problem discussed in this thread:
You might need to start from the top of that, basically Windows gets confused between “Let’s Encrypt Authority X3” which is what it should be using here, and “Let’s Encrypt Authority X1” which is no longer the right thing. So it sends X1 but the Android (and SSL Labs) system rightly expects to be given X3 and objects.
You may find some or all of the instructions in that rather long thread helpful.
If you’re not running Windows on your server (you didn’t say) please explain more about the server.