The response "SERV NOT ALLOWED" is coming back from the gateway, RapidConnect.
Please make a new test merchant on sandbox, and try a few different cards. My teammate who smoke-tested Apple Pay and Samsung Pay on sandbox found both to be in working order; however, one of the cards in my own Apple Wallet was declined (albeit with a different message). It's possible that some cards are more particularly sensitive to being run in a test environment.
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