Problem with iPod sync after migrating library

I’ve just transferred my iTunes library to a new MacBook Pro. Although most data copied across OK it has removed the list of songs which I had checked/ unchecked to synch with my iPod. As I have over 28,000 songs in my library I would really like to avoid the need to painstakingly manually uncheck the songs I don’t want to synch. (My history of ‘plays count’ also failed to copy across.)

Further background (if it’s relevant) is that I previously kept my media library on an external drive as I ran out of memory on my old Mac.