You use other plugin for PayPal Smart Payment Button, this other plugin loads PayPal Javascript library with other parameters, disable it.
Please do it and write me about result. I upgraded many APIs
Plugin supports Google Auth2.0 and Google SignIn
Can you try to use Google SignIn ?
Read this article
https://devblogs.microsoft.com/aspnet/upcoming-samesite-cookie-changes-in-asp-net-and-asp-net-core/
Install ASP.NET Core patch and tryit
I tried to login and I didn't see any error message.
But I was redirected to this page
https://www.mercadone.co/storeclosed