As a thought if you want to test it take your card to Best buy pop it in one of their display cameras and format it and then you could try it for free.
I have the micro SD cards and that's what I formatted and as I said it didn't matter what adapter I used nor did it matter what version of micro SD card so long as it was reformatted in the Canon Rebel it would then work in the Canon HF-R800.
Hello, I have 2 Canon Vixia HF-R800 and had the same issue with both, I many kinds of cards and some would work and some did not at varios times. I was able to determine that if I formatted the cards with my Canon EOS Rebel T6 then all my card worked...