Two things that come to mind are insufficient heat(temperature) for growth and root or corm rot. With other bananas nearby growing fine,its not very likely to be insufficient growing temperatures although i have read that Mysore is more heat demanding than other varieties. A problem with the root system might be more likely such as root or corm rot or even a still establishing root system if its a new pup and hasnt ever grown for you since you got it.
Does it maybe stay constantly wet at a certain part of the root ball due to bad soil? If it had any rot when you got it,that could be inhibiting its growth as the temperatures you keep it may not be enough for good growth and so not good enough for it to deal with its problems easily as it would do in good growing conditions. Also rot may have set in due to constant moisture and low temperatures without too good soil aeration/porosity.
It could also be due to being too dry such as if the soil has dried too much compacted that its not moistened properly during waterings. That would keep the plant looking good and living off its reserves from the occasional waterings but stunt its growth.
The plant may also be choking.
The above are just some ideas on what could have caused that. You should be able to figure it out by examining your plant and soil for signs of the above and maybe see something you may have missed so far
I know i found my bananas had compacted dry soil on half their rootball when i got them out of my basement,something i hadnt noticed previously.
I wish your Mysore starts growing again soon!!!