not able to force into mobile mode

[MyBrainIsFull]

Hi anyone seen a phone not being forced into mobile mode?
NT 8-65

IMAGE 1
This is a Samsung S4 being mirrored onto a pc
The menu is tiny
the ?_mobile_=1 does not force a large menu to appear.
phone stays in desktop mode

Testing   p_web.IsMobile()  returns a zero   not a one


Images 2&3
On an old app I made, the exe is making the correct menu, but the login screen after this is blank
This is the bug my customer is experiencing, blank screens on mobile

Duplicated the error on an iPhone

UPDATE
Image 4 shows another app that DOES show the mobile menu, and IsMobile = 1
Its screen is the same as my customers bug - that is - the login screen is missing  - here the image shows the phone on top half of image with a login button but no entry fields
the desktop is shown below,  as expected