We recently purchased your M2OneStepCheckout version 2.2.2. Unfortunately, it stops the PayPal express window from opening for Logged In User and we can't use PayPal express.
I tested with deactivating plugin and it works ok with default checkout.
This issue is caused due to our module's bug.
The root of this issue is that the module checks the shipping address for the logged-in users, but if the logged-in users do not have the shipping address already, it will show the issue above.
We would like to give the solution to hot-fix this issue.
We have made a change in this file: app/code/Bss/OneStepCheckout/view/frontend/web/js/model/set-payment-information-mixin.js
Please check and replace this fixed code on your site.
If you need any further support, please feel free to contact us.