The purpose of the reverse polarity fuses is ONLY to protect the power converter from "reverse polarity" should someone accidentally connect a battery to the converter with "power leads reversed" (Positive to negative terminal and negative to positive terminal). Remember that in an RV electric system, the negative battery lead is white and the positive battery lead is black. That leads to significant confusion when new owners attempt to compare it to an automotive electrical system where red is positive and black is negative (just the opposite of an RV).
From your description, someone accidentally "touched" the battery terminals to the wrong leads (it only takes a second) and the fuse "blew" to protect the converter from damage.
Without those fuses, the converter is "electrically disconnected" from the battery. There will be no battery charging capability and the only 12 volts you'll have is when you're plugged into shore power. DON'T activate your slides or power jacks with those fuses blown because you'll overload your converter and possibly cause it to be damaged beyond repair.
ADDED: You can download the owner's manual and specifications information on the WFCO 8955 here:
http://wfcoelectronics.com/product/wf-8955-55-amp/ Just click on the "DOWNLOADS" tab and follow instructions.
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