DS says no card inserted but my R4 IS inserted! HELP!!

Yep date's can also be over looked xd.

 

I had this problem.
First check regular cart works and the SD is detected in another device. If not, your DS/SD is busted, Replace as required.

If a regular cart is detected and your SD works, carry on.

I will write how to insert an effective shim.

Pry open the R4, it has 4 plastic pins that will snap open. Start at the side and work your way round slowly.
Do not bend plastic.
Keep working the case open until it comes off
Cut 1-2 peices of square paper small enough (doesn't have to be exact) to fit in the case.
Place the on the flat side of the case so they face the silicon. NOT THE CPU CHIPS.

Be sure the paper is low enough in the case so that effects the gold contact pressure. This is the likely reason why it has failed.

You may have to adjust this pressure over time with more ridged items or pressure.

Feel free to puncture paper with the plastic nipple or pin that may be holding the chipset in place.

Snap the case back together.

If it still doesn't work your R4 is likely faulty.