Hi,
What font are you using ? Are you sure it handles Arabic and contains the necessary glyphs for "محمد" ? Here is a link to the article on Texts and Fonts in the online documentation. I was able to display a text with the font Noto Naskh Arabic (look online for NotoNaskhArabic-Regular.ttf) but I cannot read Arabic, so I cannot vouch for it.
Did you make sure to edit the "Wildcard Ranges/Characters" sections in the "Typographies" tab under the "Texts" settings in TouchGFX Designer ? If not you will not have the characters needed by the application (this is used to save space by adding only the characters you really need).
/Romain
