Quick action availability with record types
Key Takeaway
Users see a quick action assigned to a record type only if they can access that record type. When users can't see a default global action, the cause is the action's record type assignment, not the page layout.
You can assign a quick action to a record type to control which users see the action. Default global actions are assigned to the hidden Master record type, so they can disappear in orgs that use record types.
Record types can change which quick actions users see
If a user doesn't have access to a record type, any quick action assigned to that record type isn't available to them. As a result, one page layout can show different quick actions to different users.
For example, imagine a page layout that holds some quick actions with no record type assigned and some quick actions assigned to Record Type A. Users without access to Record Type A see only the quick actions with no record type assigned.