GWWEB Problems with edge and on iPhone

One of my clients complains he can not send mails, add appointments in GWWEB.

Latest version of GWWEB, latest patches as know so far.

If using the edge browser default on windows, the blue button on the left above the folders is missing.

On the iPhone there should be a blue button on the lower right corner as on my Android phone, do create mails, appointment etc. it is missing too.

Even on my Android phone  ver. 13, the blue button on lower right side is not seen totaly, just the upper 20% is seen.

That should be fixed.

On my Mac everthing is fine with Chrome and Safari.