Dear Eowyn,
X2Pro and X2ProLE are the older legacy products, X2Pro5 was built for the new Apple chip set, it is a different product, there is no upgrade path between x2Pro/X2ProLE to X2Pro5 the only upgrade path is between X2ProLE and X2Pro, which is still available on the App Store.
If you logon as the same user you used in the AppStore when you purchased it will show which products you have purchased, if you purchased X2proLE, it will say so. If not you will need to go back to the AppStore as they have sole control over all user data, logins and commercial details. Unfortunately it is not something we can help with.
In the past where this has happened the user was using an older AppStore account and once they logged back into that they could see what they had purchased as that user, at some point over the years they had created a newer user.
Yours Sincerely
James.