syncing ipad to iTunes error message

I have a new MAC and an older iPad. I initially synced it, but, now it will no longer let me do that. I open the iTunes, can see that the iPad is connected, hit the sync button and then wait. It goes through steps 1 and 2 and then flashes to the step 5 of 5 and I get the following error message:

could not back up the iPad because it is not connected.

Turned off MAC, turned off iPad and still not able to do it getting the same error messages. Any ideas? Thanks