"Spraying solvent into the bolt" could cause more detrimental than helpful. Well, assuming that the bolt is going into full battery, and, the hammer is dropping properly, apparently the FP isn't hitting the primer. So, either the 'nose' of the FP is broken off, or, there's so much gunk in the FP channel portion of the bolt that the FP cannot move forward enough to contact the primer. First thing I would do is remove the bolt and give it a complete cleaning with Gun Scrubber and an air hose to make sure that it is perfectly clean and there's no crud plugging the breech face. If that doesn't do the trick, I'd be looking real close at the FP itself.

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SIC SEMPER TYRANNIS