Paypal payments no longer work

Hello,

on our site we use both paypal and stripe as payment systems. The base currency is CHF (Swiss Franc).
For quite some time now when I use the Multi Currency plugin, it does not work with PayPal. Instead when I disable the plugin and customers can pay only in CHF, then it works.
With stripe it has always worked with different currencies.

We have tried with both paypalcheckout and standard paypal as a plugin.

What could this be due to?

Thank you.

With best regards