Check your returnUrl! It should contain your app's package name appended with "://paypalpay".

[EmedStoreIT]

Error: java.lang.IllegalArgumentException: Check your returnUrl! It should contain your app's package name appended with "://paypalpay".

I am using com.paypal.checkout:android-sdk:0.8.8

This error occurs every time in the portion of the setting Paypal configuration.

Return URL in code:

Return URL in Paypal console:

[chpypl]

If your application ID contains underscores then you need to modify the returnUrl so that it forms a valid URI. For details, see the docs regarding Customize return URL.