Part of the problem here is the Cameron-enacted Fixed Term Parliament Act. In the old days, if the government lost a majority of Parliament, a vote of no confidence and new elections were a matter of course. Now, the government and the Parliament majority are at loggerheads, and an election is being vetoed by the Parliamentary majority, which is a very unusual situation in their Parliamentary system (not of course for us with a Presidential constitutional system).
I don't understand British politics, but it sort of sounds like Parliament has said they don't have confidence in Johnson, but they don't have confidence in the voters, either. Sound just like the US House of Representatives!