Rescan does not detect card. Please help.

[Doodeedoo]

I have been using Rescan for several years without a problem. I am using windows 8.1 and the laptop has a SC card slot. I am able to see the card and its files with Windows Explorer.
When trying to download data today, the program does not detect the SD card.
Get the following message from Rescan:
There are NO devices available.
Connect a flow generator or data card and try again.

Any help will be greatly appreciated.

[Doodeedoo]

Resolved. After trying a number of possible fixes and searching past posting on the topic I ended up doing the following:
1. Re-inserted card in the machine. Got "Invalid card" message with "Erase" Yes/No.
2. Selected Yes, and "Erased" the card.
3. Invalid Card message no longer appears.
4. Tried ResScan again, expecting no data as I had erased the card.
5. ResScan recognized the card and (contrary to what I'd expected), downloaded the recent data.

I'm not sure why, but it did fix the problem.