I have read through the previous posts with this issue and have not found a solution to my customer's login issue. I have verified that she has created an account in our Shopify store (and we do have customer accounts activated in our store.)
Customer has reported that she has experienced the following issue several times in the past: She attempts to make a purchase, then when prompted to login, she enters her password, then receives the "incorrect password" error. She then changes her password, and again attempts to login again, only to receive the same error. She has tried logging in on her Windows laptop, her iPad, iPhone and Amazon Fire, all with the same results.
May I privately send you her name and account email address to troubleshoot this issue?
Welcome to Shopify Community. I'm sorry for your inconvenience.
You should check you store status under SHopify Status web page.
You could contact Shopify Support under this web page with your store id: https://help.shopify.com/en/questions#/login
Live chat or email: https://help.shopify.com/en/questions#/contact