Thank you for contacting us, and I’m sorry to hear about the issue you’re experiencing after the recent iOS update. I'm not sure I'm fully understanding some of what you have written here, but if you are using mSecure 5 for the first time, you should be able to simply sign up for a new account, and after choosing a sync feature, the app should ask you if you would like to transfer your information in from mSecure 4. The data will be migrated after say yes to the transfer.
Were you able to set up a new mSecure 5 account, and did your existing data get transferred?
The typically way to update is to upgrade the same app. However, with mSecure 5, we created a different app entirely so that our customers wouldn't be forced in to upgrading to a new version of the app that was a paid upgrade. Since the app is a different app entirely, it's not tied to mSecure 4 in any way, and it works much differently. You will need to create an account in mSecure 5, and after doing so, you should be able to migrate your information during the account setup.
I hope that all makes sense, but if not, let me know, and I'll provide clarification. The short answer is, you should tap the option to Sign Up for a new account in mSecure 5. It will have no adverse effect on the data stored in mSecure 4, and after choosing a sync feature, you should be asked if you would like to transfer your information in from the old app.