New glow plug issue

[Cainon]

Put new glow plugs in. The clips will not lock in. No I did not buy cheap autolites. 85 6.9l idi f350. Tried clipping back on old plug and it works fine. So clip is not broke. But will not lock into new plugs. Side by side plugs are identical

 

[riphip]

When I used the older plugs, before my upgrade, I used pliers to tighten the grip on the female connection very lightly until it stayed on to my satisfaction. Too much and it will smash or break.