I did not travel with any animals - I had 2 11-year-old grand-daughters. You could call them directly as suggested or use the 800 number to find out corporate policy.
Best to call them directly. I had a service animal and that was no problem.
A couple of guests had pets when I stayed at this Motel 6, and their web site indicates that it is a pet-friendly facility.
Get an answer from Motel 6 Seattle East - Issaquah staff and past guests.