So I live in Canada further north I've been keeping my mint plant by our window sill I have a pretty big tree out front partially blocking the sun and I'm not sure if my plant is dying from lack of sun, to much sun??, temperature, cramped are, lack of water or excess water like I've started watering it more but the leaves are still dropping (it is on a windowsill that is above my radiator but I've kinda boxed in the top portion of the radiator so I could have plants on top) it generally falls pretty dry to the touch for the soil I have it in a pot with gel beads that retain water and it is still in a compostable pot holder it is in a pot that is around 6 inches wide. Please help me fix this before it dies cause I'm pretty sure it should survive year round when left indoors it doesn't seem to want me to post a picture here is a link to a drive with pictures https://drive.google.com/folderview?id=11bgPcMUOupF3Am4sfpfMOlnmjxBvEf9R
Mint is usually a very cooperative plant, roots easily and produces lots of leaves without complaint but does not like to live in an overcrowded pot. It will survive quite well in low light, so that is not the issue, nor is the water available.
My solution to your issue may seem drastic but I think would be sure to improve the situation - the root ball needs to be broken open, healthy roots extracted from the root ball and transplanted, with or without top growth, to fresh soil, kept moist and in a few days you will see new sprouts appearing. The current root ball is probably very dense with roots and may be hard to break open, so if you have a solid flat surface that is easily cleaned afterwards take the root ball out of the pot and throw it (the root ball, not the pot) hard against the flat surface. This will break open the matted roots and allow you to search for thick, healthy rhizomes that can be the start of new, vigorous colonies of mint.
Once you get the hang of the process this can be repeated two or three times a year, producing more fresh, large mint leaves than you thought possible.