Export activation

Hi, so I made an account not too long ago and started to edit/export projects. But recently, after many prompts to update my hitfilm express, I decided to delete then reinstall the new version of hitfilm express to avoid having the notification. I just finished up a project when I realised that my export was unavailable. It says that I have to activate to unlock but when I put in my serial code displayed on 'account' (I'm using the same computer), it tells me that it is a different version of hitfilm. This means that I can't activate the export or get another serial code and wont be able to export ever? I can't reinstall the older version so how am I supposed to export?