I didn't use glue. I put a big blob of blu tac onto the sensor and stuck it to the mirror casing. As there is not much room for manoeuvre in there the sensor is sandwiched between the windscreen and the casing. It seems to be holding.
Do your wipers come on automatically? My ones have to be woken by moving the scroll wheel. I think the sensor position needs adjusting.
just refitted mine at autoglass the nice man did it for free but I guess he could have easily asked for a tenor .I watched him very carefully and got the name of the glue they ues its Loctite 317 used in conjunction with Loctite 734 basically make sure the bracket and screen are really clean I used some white spirit then but some 317 glue on the bracket then once the screen is dry spray the Loctite 734 on the screen and attach the bracket you have a few seconds to get it in the right position and its stuck perfect. it does say that its set after 2 mins but I left it 24 hours in the sun (apparently works better in warm dry weather )
when refitting the sensor and gel front make sure its clean . I put a little blob of kygel behind the gel that fits on the front and pressed it which help when fitting to the screen as kygel is conductive so to make the sensor more sensitive as in factory fitted. hope this helps and please no jokes about the kygel I use it with my ab belt hence the reason I know its conductive .