If a single customer dropped you because he now has Teams for free your product was a failure for that customer anyway and he just suddenly realized you offered him no value.

Just look at https://taskulu.com/ and tell me how Teams even competes with you. Your real competition was Jira and customers dropped you because Jira was a superior product and integration with Teams gave them everything you offered and a chat application separate from project management is an all around better option as there is a single chat for all employees, regardless of them using the project management tools.