I would like request adding the Fidelity rewards credit card (fidelityrewards.com) as a linked institution. Thank you.

Fidelity Investments doesn’t work with Plaid. But it worked with the other service you had to link as an investment account. It seems like you ought to be able to use that service to link the Fidelity cash management and Visa card to your system so us Fidelity people can use your app.