That looks like it's the SD card indeed. Did you know there are fake cards, that say 128 GB, but are in fact only 16 or 32? You can't use the part that doesn't exist.
Be sure to buy from a reputed maker in a reputed shop.
I have recently been trying to transfer about 5k songs from the my pc to my external SD card 128gb to then put into my phone. I have had nonstop issues with this, as when I try to mass transfer all 25gb over everything works fine until I try to play said music. First I try mass transfer using micro sd to USB port then into phone and try putting SD into phone and then mass transfer same issue with playing as when it tries to read the track it says '' sorry this is player does not support this audio file '' with the <Unknown> shown in the track info. Now this happens no matter which way I try to transfer the files either through mass transfer in one folder or all detailed through 15 folders comes back the same way, same either way I transfer either with micros SD to USB converter, SD in phone and have USB hooked to phone and try to transfer, and even tried wireless transfer with the web pc suite app always comes back with the same result in that some songs work about 1000 to 1500 all the rest come back as '' player doesn't support audio file '' with the <Unknown> in the description. Starting to think it's the SD card but everytime I scan it it comes back as nothing wrong with the device. Was hoping someone could help me merge out, much appreciated