Must i deactivate hitfilmpro befor change or is it not necessary..
Not required, although you will need to reactivate Hitfilm and Plugins after the swap. I just upgraded my CPU and had the same issue. It reverts to demo mode but thinks it's activated. So just deactivate it, reactivate it and all is well. Had to do that for all the versions of Hitfilm and Plugins I have on my PC.
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