B&K Ref. 20 problem

I recently purchased this processor to replace a Lexicon processor that died. It may be an interim step while I decide if I want to invest in a new processor with HDMI. I do not run a center channel and have the B&K setup for 2 front and 2 surround. My problem is that I’m unable to get center channel information through the front L&R speakers using the digital outputs from either my Fios box or BD player. My BD has 5.1 out so I setup the B&K that way playing movies and center channel information comes through loud and clear. My Fios box does not have 5.1 so I’m forced to use the audio digital outs. Video for both Fios and BD is through HDMI direct to the TV. I never had a problem setting up a phantom center with my other processor(s) and did not change any settings on the Fios box or BD digital outs while setting up the B&K, so it appears to be something in the B&K.
Can anyone suggest a troubleshooting procedure or a particular setting for the B&K to correct the problem?