Stock buys below 1

I use an iPhone and when buying stock I cannot select anything below a whole share in some cases. I haven’t identified what causes it but fractional purchases can’t be made using this way.
The slider starts at 1 and the number pad lacks a point eg .5 to get to that.
Any ideas, or can this be added to the number pad?

What ticker are you looking at?

Seems only assets that are available in fractional form have the . on the number pad. If it isn’t there then I’d suggest the case is that the share you are trying to buy isn’t available in fractional form.

I’ve just checked this and yes it’s correct. Some companies only trade whole shares.
Learnt something today.