Hello together,
I have found a solution (at least for me) how to get from Pro to Premium via a one-time "upgrade", because I actually did not want to switch from Enpass.
If you buy "Enpass Lifetime Premium" from the Enpass website with the existing email address of the Pro account, the Pro becomes Premium (after a few minutes this is then displayed in the apps). At least that's how it worked for me.
At the moment there is the "Happy Holiday" promotion, which makes Premium a bit cheaper.
For me, the in-app offer in IOS to switch from Pro to Premium by means of a subscription