Student or Learner
This is clearly an ungrammatical sentence:
"Freddy would like to see the home-opener, but tickets are unable to be purchased by him."
An obvious correction would be: "Freddy would like to see the home-opener, but is unable to purchase the tickets."
But how does one describe the grammtical problem in the original sentence?
That Tickets do not possess the property of "ability"?
But then: "Tickets enabled Freddy to enter the gate."
I apologize for the inartfulness of how I pose this question, and I hope someone is able to get past that and offer clarification.
Your first suggestion is a good one. Tickets don't have the ability to do anything or to not do anything.
With your example "Tickets enabled Freddy to enter the gate", it should be "Having tickets ..." or "Possessing tickets ...". I would also say "... enter the park/stadium/grounds" or "... get/pass through the gate."
Remember - if you don't use correct capitalisation, punctuation and spacing, anything you write will be incorrect.