New device stuck after firmware upgrade to 7.6 - Fortinet Community

If you are currently on FortiOS 7.0, plan a migration to 7.2 or 7.4 before 7.0 reaches end-of-support. If you are on 6.x, plan an immediate, carefully tested upgrade path to 7.2 or 7.4. Your network’s security depends on it.

to see if you need "interim" versions (e.g., upgrading to 6.4.x before moving to 7.0.x). The "Run Image" Trick

Upgrading your FortiGate firmware requires careful planning and execution. Follow these best practices: