This eShop errors seems to appear if you try to unlink NANDs and then format sysNAND (this also logs out of NNID if connected to internet). Even though the NNID was set up on emuNAND it will no longer work and when trying to access eShop it will show that exact same error I think.
Solution for that is to login NNID on sysNAND (create another emuNAND on a spare console SD card, using the now-formatted sysNAND) then on that emuNAND login to NNID. Once that done you can put back your original SD card that has your previous emuNAND and eShop should now work as normal.