Your error message might not exactly match "525 Origin SSL Handshake Error" it could be "Error 525 - SSL handshake failed" or something similar.
This issue can happen very rarely if our SSL certificates (the things needed to make a website https rather than just http) expire. They are set up to renew automatically (to prevent this from happening), but for some reason something went wrong and they did not renew.
If this is the case we are normally notified immediately and will have it resolved in a couple of hours. Once the SSL certificates have been renewed, please sign out, clear your browser cache, then sign back in and retry. That should resolve the issue.
Instructions for clearing your cache can be found here.
If after a couple of hours you retry and you are still receiving the error please contact our support team. Please quote the error message. We will already be aware of the issue, but it will mean we can respond to confirm once the issue has been fixed and you can retry.