Ethanol in fuel absorbs moisture for the air. That jelly looking stuff is most likely the result of using E-10 fuel which has undergone phase separation by absorbing moisture from the air or water than made it's way into the tank or your storage container. It's also possible that the ethanol in the E-10 has dissolved some of the rubber fuel system components, not necessarily enough to prevent them from working, but enough to cause the darkness you see in that jelly. That darkness could also be rust because ethanol absorbs moisture and can allow metal fuel system components to rust and corrode.
About all you can do at this point is thoroughly clean and inspect the entire fuel system, including injectors. The fuel pump may have to be replaced if the pump has deteriorated internally. After cleaning perform a fuel pressure test to assure the pump is up to snuff. Volume produced by the fuel pump isn't enough, fuel pressure must be correct for fuel injection systems to work. I suggest a digital service manual available as a download for about $10 to assist with procedures and specifications.
You can prevent this in the future by using non ethanol fuel. If that isn't available in your area there are some things that will help, but not totally prevent recurrence of the problem.
1) Use a fuel stabilizer designed to prolong the life of ethanol fuels. There is a year long testing done by Taryl Fixes All on YouTube where he tests various fuel stabilizers that might be worth watching. Before non ethanol was available in my area I had good luck with the StaBil Marine Ethanol Treatment, but I also heeded the following cautions. 2) Don't store gas for more than 30 days in a storage tank or allow it to remain in your vehicle fuel tank for prolonged periods. If prolonged storage is necessary and non ethanol fuel isn't available in your area drain your tank and add a gallon or 2 of TruFuel or a similar product and run the engine on it for a few minutes before storage. 3) Keep your fuel tank full as often as possible and during storage if left with ethanol fuel. This allows less air space for moist air to accumulate so condensation inside the tank with temperature changes becomes less of a problem. 4) If possible store your vehicle inside a space with a controlled environment with stable temperature and low humidity.
Ethanol in fuel is not good for the environment or for engines. We get away with in in our regularly used vehicles because it doesn't stay in the tank long enough to absorb enough moisture to undergo phase separation or deterioration since we use it up regularly and replace it. When stored for long periods it will cause problems even in our regularly used vehicles if precautions are not taken. Modern vehicles have a slight advantage in that their fuel systems, including the tank, are fully sealed to prevent evaporation of the fuel for emission requirements, however they are sealed only in that they won't allow vapors out, they will allow outside air in, and outside air brings with it moisture which turns to condensation when temperatures change. Even when precautions are not taken in our regularly used vehicles we often get way without problems because the fuel systems have larger openings in fuel system components and larger capacity filters. Small engines are another matter. Fuel system component openings are smaller, filters have less capacity and may only be screens or socks in some cases, plus equipment with small engines is often left unused/stored for long periods between uses, for example a snow blower used regularly in winter sits in disuse the remainder of the year. This is a recipe for problems when ethanol fuels are used and left during periods of storage. Engines with carburetors may have fewer problems becasue the float bowl has the capacity to keep some nastiness below the main jet but once it builds up to the level where it can be picked up by the main jet trouble is certain to occur.
