Consistently "flat" prints is a classic sympton of fogged paper and the cause often is the safelight as others have mentioned. So the first thing I'd do is a good safelight test. The test shouldn't be the "put a quarter on the paper" thing which is useless but a test as described in Ansel Adams' "The Print" or that is (or at least used to be) described in the Kodak literature and on their web site.
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