Mortar is not solid after 48 hours !! Normal?

[Noah1234]

It has been 48 hours and the mortar still turns into dust when rubbed between my finger.

Is this normal?

The temperature has been between 7 to 17 degress C.

They are the top 2 courses of my shed, I don't want to put the flat roof if there is a problem with them.

Thank you!

 

[EddieM]

No, not normal, either wrong mix or cement has gone off.

 

[mattylad]

If its still not set, take it down and do it again.