My 4GB PNY Optima sd card will not read

Try the 4GB card in some other reader, or your camera, to confirm that it does work.

It's possible that your card-reader will not support anything over 2GB.

SD cards are not created equally! There is so much more to know than just the capacity.
There are many things about SD cards most people are not aware of. After having numerous problems with my cards, I thought I would share what I learned, mostly from online articles, trial and error!
There are SD cards (Secure Digital)
SDHC cards (SD high capacity)
and SDXC cards (SD extra high capacity, high performance)
Speed Class: There may be a C with a number inside the C printed on the card, (or a U with a 1 in it) - if there is no C or U on your card, it is a C2 card.
C2 is for basic data and photo use and has a slower processing speed.
C4 and C6 are acceptable for up to basic video.
C8 and C10 are high performance, fast processing speeds - and cost more.
The U1 symbol indicates fastest processing speed available, and will cost the most. For large size, HD videos.
If you are trying to use a basic SD2 card (no C rating or C2 rated) for a high quality or high speed video or large RAW photo, you may have problems with your device. The card may not be able to keep up speed-wise. These are generally older, or lowest priced cards. More information and photo examples on the speed class here: https://www.sdcard.org/consumers/speed/speed_class/
Your device will read SD cards up to the capacity it is capable of. A device with SDHC capability will be able to read basic SD cards, but might not be able to read an SDXC card, so you may think you have a defective card when you actually just have a device that does not have the capability to read it.
If your computer's SD reader or peripheral card reading device has an SD card reader and it cannot read SDHC (high capacity) or SDXC (extra high performance/capacity) it will reject or not see the card and you might think you have a defective card. Put the card in your camera or other device you are going to use it for, and then using the USB cord that came with the device, plug that into your PC. The PC will be able to read the card that way, edit it, etc.
After copying all files on the SD card to your computer, you may wish to format the card before using it again. When formatting the card, IMPORTANT: Make sure you have copied all the data you want to keep onto your hard drive, and make sure it is formatted FAT32. I kept formatting a card FAT (which was the default for this card), and the recordable capacity of the card kept getting smaller...and smaller...a 2GB card was only allowing 350, 250, 125 MB of data to be stored on it! I kept hitting a brick wall trying to copy files onto it. I kept formatting the card, thinking there was some de-frag issue or corrupted portion, and the capacity of what it would store kept diminishing - until I formatted the card FAT32. ONLY THEN was the card able to store to its true capacity. I was able to do this in Windows in Explorer - right click the drive the SD card is in, select Format, verify the Capacity (card size), verify the File System (use the pulldown menu to select FAT32 if it is not selected), and then click Start and allow the computer to remain undisturbed until the format is complete. I found a web page that covers this: http://pvillecomp.com/
There is an SD website that offers a download for proper formatting of your SD card, with downloadable instructions. I was using Windows to format my SD cards, but the SD website recommends using software that specifically formats SD cards. Here is the site: www.SDcard.org. Click the Downloads section.
Some older devices can only handle smaller SD cards (2 GB or smaller), so if your device cannot read a particular SD card...check your owner's manual. There is usually a limit to the size, capacity, speed, type, etc. of the cards each device can handle.
It is also possible to partition an SD card so it can be read by more devices, or separated for organization purposes. I prefer smaller SD cards when possible to avoid a huge loss if the card becomes damaged, lost, etc., but for those who have cards that are 16+ GB in size they may want to partition them. Here is a website for that:
http://forum.xda-developers.com/showthread.php?t=267475
Hope this helps!