App License key - suggest a logic

ajayjain

I have created an app, which expires in 3 months
I have added a functionality where I give a key to user and app can be extended further- by 6months or 1 yr
it is working fine but if app is used by a company on multiple tenants then same key can be used
how can I avoid this?
I can ask tenant id and generate a key based on that?
SaaS based does not allow encryption based on personal key?
I do not want to use stripe or api to check the key, it must be something within app.
Please suggest a logic,