After you recover files that were deleted, how do you open them (used recover software)?

I can't open any files that I recovered

Well just because they were successfully recovered doesn't mean that they were recovered successfully. What I'm saying is, they're probably corrupted data, so they can't be opened. Another possibility is that they're just missing their file association. So basically, instead of double clicking the files, open the program, and go File>Open and then try to open the file that way. Another possibility is that the recovery software requires you to do something else after getting the data the file is made of, basically some way of translating that data back into the file it was. I suggest reading whatever documentation goes with the software you used. Check their website, that sorta thing.

the reasons maybe:
1. the version of the recovery software that you used is a trial version. it means that you can only see the recoverable photos, but not save. to save the photos you need to buy.
2. the photos may be corrupted. the corruption reason may be due to data overwriting.
3. the software quality. if the software is not a professional one, the quality maybe not so good.
what you should do:
1. check if the version you use is trial version, if yes, you can try to get the full version.
2. if the version is the full version, you should try to think if you have saved any new data after your data loss.
3. if you did not save any new data, maybe the reason lies in the software quality.
if the data is really import for you, I suggest you use professional photo recovery software. My recommended one is Wondershare Photo Recovery. It can recover lost photos,videos and music.
Get the free trial version from http://www.disk-utilities.com/photo-recovery/index.html
You can preview your photos from Preview Thumbnail to check if all the photos you need are recoverable and evaluate the recovery quality before you buy.