Problem with customer accounts (customers saying not able to log in)

Hi ! I am having a problem I think with the customer accounts.

I have had a few customers writing to me recently that they cannot get into their account. I’ve not had a lot of recurring orders for months and now I am wondering if this is the case.

Has anyone else experience it ?

When I looked into it, I noticed that the customer accounts have changed. Customers can now enter their account with a code sent to their email. But I still use the default (classic) method of email/password.

Did these changes to customer account by Shopify cause problems for previous customers ? Was there a bug ?

Why are customers saying they cannot enter their account ?

And if so, how do I remedy it to stop losing customers ?

Thanks !