A crossgrade means that you then would own ozone advanced, the base product you need is the one you own and you don't need ozone in your native account. You can check it for yourself to be absolutely sure on the shop website, you have to be logged in and then you'll see if you can buy the ozone advanced crossgrade.
i ran ozone 10 advanced in logic from it's release until the ozone 11 release without issue (11 is working fine now). validation took a loooong time in final cut, but everything works (at least, in logic, where i use it, along with vocalsynth and nectar 3). fwiw, i needed a previous version of nectar 3; if you use that, 3.7.0 works here).
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