How long has it been in the bottle and how big is the beer (abv)? Bigger beers often need extended time to bottle carb. In any case, there's no harm in letting it sit and see what develops. Leave it for a month and open another bottle then and see if its carbed up, perhaps.
I'm not immediately thinking of how the flavor and carbonation issues could related.
Its always so hard to diagnose problems through flavor descriptors. Could the citrusy flavor actually be a part of the pumpkin flavor, a fruit-like flavor but not really citrus? Is the sour flavor really sour (as we usually use it in brewing terms, like vinegar is sour) or could it be more tart or astringent?
If it really is sour, that's a sign of an infection. If it was in two bottles, it would be unlikely to be a result of wild yeast/bacteria in the bottles but was likely present before you bottled. It have been present in your bottling bucket, for example, but you didn't taste it because it hadn't had time to develop yet, but it has developed now that you've bottled.
So, if it were me, I would have another, experienced brewer or two taste the beer (uncarbed if necessary) to see if it really is sour. If it is, then I'd go nuclear on my equipment - throw out any and all tubing, replace any plastic buckets, replace racking canes or autosiphons, bottling wands, etc. Anything else, I would bleach the hell out of it, then rinse very thoroughly.
Its possible though that nothing is wrong with the batch and after its carbed up it will taste just fine. Carbonation influences our taste perceptions quite a lot.
