Eugenia O wrote:
If client with payment method not verified invites me to send a proposal, how could I politely decline the invitation without losing my rating and reputation on Upwork?
Declining invitations does not affect your rating or reputation at all.
There is nothing wrong with clients who have not yet verified their payment method. As long as you do not accept any contracts before payment methods are verified, talking with such clients is fine.
I have made many tens of thousands of Dollars from such clients.