Collaborate 4.3.12 is a bug fix release which was deployed to multiple clients last weekend. Unfortunately, in resolving one of the critical issues, an API bug was introduced. This is causing our clients to receive a 403 forbidden error message when calling the iSheets API's.
The technical team have investigated and resolved the bug in release 126.96.36.199. This point release will be deployed to all affected instances this coming weekend on the 28th of July and will resolve this API issue. If there are any urgent concerns and you would like to upgrade your instance earlier then please get in touch with our support team at firstname.lastname@example.org to schedule the upgrade.