We took this site over from another user.  He had originally purchased the wpdatatables license.  The renewal is coming up so we purchased a new license.

I tried to deactivate the current license to activate the new license.  Upon selecting the deactivate button I get the error "Error! unable to deactivate plugin.  Please try again later."

After refreshing the page I get an activation box.  I entered our new license code and now get the error "Error! You have reached maximum number of registered domains."

Thanks Milos.  Still having the issue.  Things I have tried.

1. Added your code to  to line 1059 with no luck

2. Also added your code to line 1164 with no luck

3. Deactivated every plugin with no luck

4. Removed SSL from site and tried to activate the license with no luck

I am still getting an error deactivating the old license before trying to add the new license.  I browsed the database in hopes to see a license I could remove and readd and didn't find anything.

Thank you again for your time!

Milos, 

Thank you so much for such in-depth instructions.  Downgrading to 3.5 worked.  I will now upgrade the plugin.  

Thank you for all of your help!  

Jason

Milos,

Thank you again.  I will post a positive comment.

Jason