There's a chance his injury isn't covered by insurance since he had concussion issues prior to us signing him. We used to have some threads that went in depth on how the insurance worked, but they didn't get migrated to the new servers it seems, but from memory:
-The league takes out a contract for the whole league to keep costs down.
-Teams pay a premium based on 5% of their 5 highest paid players.
-Teams are free to allocate coverage to 5 or more players.
-Max coverage is 80%, but if you opt to cover more than 5 players it is reduced proportionately
-Insurer can exclude pre-existing condions from coverage.
Coverage for concussions is/was a major issue wrt insurance a while ago, there was talks that insurers might exclude concussions outright and not just in pre-existing situations, not sure what happened there but I imagine the NHL worked something out to maintain at least some coverage.