It can take longer for a Venus flytrap to perform the digestion process if it isn’t healthy or if it is in cool temperatures. Under good conditions, a plant completes the digestion process in about 7 to 10 days. When you say “it doesn’t appear to be dissolving & consuming them,” I am guessing that you mean one of 2 things:
1) That it isn’t creating a seal when it catches an insect. If that is the case, then it may be because you aren’t feeding it live insects. The inside of the trap must be stimulated after it catches the bug in order to fully seal.
2) That it isn’t completely dissolving the insect. This is perfectly normal. Sometimes after the trap reopens in a week or so, it doesn’t look like it did anything to the insect, but all of the nutrients from the inside of the insect are absorbed and the exoskeleton is left behind.
Venus flytraps do not actually dissolve or consume insects, rather they just absorb the soft inner parts. Read more about Venus flytrap trapping and digestion.