The login for this site is requesting robot challenge to everyone and when you hit submit it just goes back to the same page. I have not seen this before and did not set it up. I need to fix this as none of my customers can get into the site/accounts
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I just spent 2 hrs on chat with Shopify on this issue to finally be told "It seems like this issue is still happening to some stores and shopify plus merchants. There is no work around time for this issue yet." and "Shopify developers are already working on this issue but there is still no update as of the moment if this has been fixed already."
I tried a brand new theme (Debut) and still have the same issue.
I discovered what I think is a new configuration setting. Go to Online Store->Preferences and then at the bottom is a setting for Enable Google reCAPTCHA on contact forms. I turned this off and it fixed my login issues. I know it might expose me to spam in the "contact us" form but I will deal with that. At least my users can log in again.