NUMBERVALUE returns #VALUE error on some machines

NUMBERVALUE such as =NUMBERVALUE(MID(B11,18,10)) works on some machines correctly whilst on others using exactly the same spreadsheet returns the error #VALUE! error - any thoughts?

any thoughts?

No - if you don’t tell us content of B11 and version of LibreOffice on different machines (having which operating systems, and, if Linux, using which packages [distro, TDF, etc.]).

Probably a good idea to provide a sample file.

… and locales set up on LO on the machines that calculate vs those that don’t.

NUMBERVALUE() takes 3 parameters, use them. At least the second, decimal separator. See help.