Could not SHARE my projects...

Okay... So I have a FCPX version 10.0. I happen to buy a second hand Macbook Pro on ebay a few years back and this software came with the Mac. I only started using this software a few months back and was able to make a few decent projects with no hitches. Meaning, I was able to finish the project and share it on FB and convert it for my i-devices (iphone, ipad). Since it became easily a favorite program of mine, I upgraded to the lastest OS Mavericks and I also made a hardware upgrade from a 250gb hard drive to a 1tb hd. Now, I began a new project. I followed the same procedures as I was doing in my old projects. Then, when it came to the time to SHARE, I kept on getting an error message about a "compression" error. I tried to fix it for hours, but no luck! After much researching, and since there was an option in the SHARE dropdown menu to forward the file to COMPRESSOR, I ended up buying the program "COMPRESSOR" at the Apple Store, cost about $49.99.

Short story, even the COMPRESSOR did not solve my sharing issue. I wanted to upgrade this version (10.0) of the Final Cut Pro X, but since it was bought by probably the previous owner of the Macbook, I could not log in to the apple id. I am desperate. I could not understand why I can't proceed when it was doing just fine a few projects back.

Was it because I changed my Hard Drive? Or the Operating System? However, those projects I made were already done after the upgrade. Help please anyone???