I've read the Microquits carbs tend to gum up if allow to sit for extended lengths of time. Refined fuel has lots of additives and dirt. Some people use a fuel stabilizer with generators because newer carbs tend to be more sensitive to dirty fuel and additives.
Onan recommends to run their generators for a least one hour each month.
However my older generation 20+ year old Onan 4000 I've allowed to sit without use for up to years and it has started up each time it was needed.
Once you get the Microquiet to turn over I would have some carb cleaner on hand. You want to make certain the carb is not all gummed up after sitting. You will want to run it for at least an hour.
Here is a link to a Microquiet 4000 service manual.
I would read through the manual and familiarize yourself with different parts and aspects of the generator, it's wiring and connections.
There is trouble shooting section (6) that includes an "Engine will not Crank" and "Engine Cranks but will not start" conditions.
Manual includes many generator diagrams to familiarize your self with it's design and it's connection to the RV and batteries.