Hi Topherstewart11 Stewart,
You do not own the tied accommodation, so if you purchased a property and you are a first time buyer, you should still be able to purchase with your life time ISA.
The age limits (18 -40) only apply when opening a life time ISA.
Please have a look at the guidance here:
Lifetime ISA
Your ISA provider should also be able to provide you with more information.
Thank you.