Why do my matches keep dissapearing?

so, its not really disappear since i got the replay, but i didnt get any rewards from it, in fact i lose sl. i dont know if this issue has been here for long or a new thing, but its starting to get on my nerves after multiple occasion that this happen. most of the time the effect is not too severe since i probably just play for like 40~ mins when it happen. but this time i played for 2 hours, and its really painful to the point when i realize, i sob. so please, is there anything i can do so that this doesnt happen to me anymore?