How to format larger cards with the Varia RCT715

To help anyone who can't format a large SD card:
I tried SanDisk Extreme microSDXC 128GB
Varia saw it as corrupt (as did my old card readers that apparently can't handle this type).

I could not mount this on my windows machine.  it also showed as a corrupt drive. 

I could not connect to my phone while the varia was in SD error mode, so the fix is:
Boot the varia with original SD card, connect to varia app, pull the SD card out, insert the new larger card.
Varia app will then tell you the card is corrupt and ask to format. Hit yes, and you should be good to go.