Stubborn laminate boards that won't lock, can I glue
I don't see gluing the joint being a problem as long as there is nothing trying to push the joint apart, other than a small deflection of the floor while stepping on it. The subfloor itself is supposed to be pretty flat, say no more than a 1/16" dip in the floor with a 4' straightedge. That was the requirements with my floor. Yours may be different. It should be somewhere on the packaging.

Other factors could cause it to separate, for example, and perhaps it really the only thing, is that the interlock that hold the pieces together failed either before or after assembly. If the high part of the interlock gets knocked off, there will be nothing to hold it together. If that is the case, and the missing parts aren't lodged someplace that forces the mating parts apart again, and there is not a place where the flooring drops excessively when it is stepped on, then by all means glue it and forget it.

If the joint has trash hidden under or in it, the glue will be hard pressed to hold it all together. It will fail with movement, the core material of most laminate flooring is not made to handle a lot of movement, let alone glue trying to hold it together as well.