Here is a link to a post that gives some basic steps to take in these types of issues.
Huh… interesting… Did you try pressing the APP button a lot earlier.. I usually press mine when the ILS signal is detected, and I don’t need to wait until I’m lined up before I press it. I leave the APP to be armed and activates itself automatically when it’s captured. You’re also a bit high on the glideslope, which is usually too late to engage it. That’s why I prefer to arm it earlier before crossing the localiser and make sure I’m already below the glideslope, not above it.
Also, try to do a…