Here is my opinion on all five:
1. Call shy........No way. Turkeys don't know we imitate them, especially only in the spring. They may not respond to a call but it isn't because they are "call shy".
2. Henned up....sort of a lame excuse because if you can call the boss hen in, he will tag right along. It't much harder because with those extra eyes looking around, you are more likely to be picked off. You can also bust them up and then start calling because they will be trying to regroup.
3. No gobbling....I personally hate these kind of days but if you are really serious, just set up in an area that they normally use and call occasionally, he may come in silently.
4. Bad weather.....See #3
5. Interference by another hunter.....That happens and really is a valid excuse although if he only spooks the gobbler and doesn't kill him, you can just cool it for a while and sometimes he will respond to your calls again.
Of course, these are just my opinions and everyone is entitled to their own.