I have some apps that won't recognize my Apple ID, even tho it is correct. Not sure what to do.

My apps wont recognize my Apple ID. I had a problem because I was using 2 different emails for apps...didn't know I couldn't. So then I created the same password for both to capture everything. Updated my software (that was part of the problem). Apps have been updated now, but I cannot make In-app purchases because the Apple ID won't work. I really don't know what I'm doing wrong. Any advice??