Cross-posted from another support thread here in the hopes that higher visibility may lead to a fix:
I may be having a related issue? I'm not sure. I'll lay out my symptoms, and hopefully someone much more clever than I will be able to address it.
Just to get the obligatory data out of the way, I'm on a New Nintendo 3DS XL US, running the latest (9.8.0-25U) firmware. I'm using a "Blue Button" Sky3DS (which I think shipped from China based on delivery time). I'm writing to a SanDisk Ultra Class 10 MicroSDHC 32GB card via a Targus-brand multi-card reader. EDIT: I'm also using Template0624. I was using an old "TransFlash" usb-to-microSD reader from my CycloDS days, and also tried with the T-Flash reader that shipped with an R4i-Gold 3DS flashcard, but those both appeared to be generating errors. Specifically, the CycloDS Transflash stick is no longer recognized by the computer at all (does not mount, basically) and the T-Flash unit generates a windows "USB Device Not Recognized" error (and also won't mount). These issues didn't start to appear until my attempts to correct my issue (described below) on Friday. It's possible I fried my cardreaders, which would be sad.
The actual issue is this: I switched from 1.06b5 to DiskWriter 2.02b1 on Friday. When I inserted the microSD chip and launched the new DW utility, I got the message that my chip was in an old format and I would need to upgrade. Okay, so I did. I followed the wizard and watched as it created a save-game backup file on my hard drive, formatted the card, then restored the backup. When I went to launch the games in my Sky3DS, I followed the on-screen instructions: Insert Sky3DS with button held down, eject, wait, reinsert, watch for blue light to flash very fast, eject, wait, reinsert and games should load. I did that, and got the fast light flash, then reinserted as instructed. Nothing.
I played around with various iterations of the above steps most of Friday and Saturday, which is what led to me getting a new card reader. This is even a brand new MicroSD card from a retail outlet (ie, known-not-counterfit). The current state of things is this: the card is formatted as FAT32, then formatted using the DW "Format" utility, games written to it, inserted into 3DS, get nothing. I can launch other (legit) 3DS games, and it will read my R4i NDS-flashcart and launch those games. If I insert the Sky3DS, I get nothing - no game loads, no flashing light. If I hold down the button while inserting, I get nothing. I eject and reinsert, I get the fast-flashing light. I eject, wait, reinsert, and get nothing.
AT this point, I think the card is working - I don'tk now that it is, but I think so. I don't know if the new DiskWriter is working, or if it's fucked up my Sky3DS to the point where it needs a new firmware flash (or if that's even possible). I've tried this with the old 1.6b5 DW as well, with no change.
Any advice or suggestions would be welcome. I'm at the point of negotiating with a local US retailer for an exchange or discount purchase of a new one. Help?