I encountered this bug myself last week and fixed it; I forgot about this post until @herb posted a comment on it.
The fix will be in CiviCRM 5.25+, but the bug is logged as https://lab.civicrm.org/dev/financial/issues/119, and the fix is incredibly simple to apply.
You don't say what CiviCRM version you have but this was fixed in 5.27.0
https://lab.civicrm.org/dev/core/-/issues/1608 & sounds similar
This patch - https://github.com/civicrm/civicrm-core/pull/18062 should improve the quality of your error logging
This seems to be an error on the paypal side.
Check with paypal, if they have blacklisted your IP.
Try doing a contribution with a different router or a separate internet service provider, i.e, a new IP that hasn't contacted paypal yet.
Front end links working again after upgrade to 5.28.2.
Note that there was also an update needed to our Mailchimp webhook for linked groups. Simply done by saving the group settings.
Fingers crossed the Paypal payment IPN link is still good to go.
Only PayPal can tell you the reasons for an account limitation and the steps required to resolve it.
PCI stands for "Payment Card Industry", and is a standards body that Visa and MasterCard and other payment card providers are part of. They created a set of standards that merchants must meet to be compliant. PayPal does not validate, and is not responsible ...