You've linked to an outdated
svmono version. (Do complain to Springer for linking something outdated!) Springer is not very good at maintainig this class, but, anyway, as these lines are written, feel free to get an updated version 5.6 from http://www.springer.com/gp/authors-editors/book-authors-editors/resources-guidelines/book-manuscript-guidelines/manuscript-preparation/5636 .
You've also forgotten to use the class option
With class version 5.6, the error occurs. Complain to Springer again; it's their fault. (In my view, they bath in money from the libraries and can allocate a bit more of it to support LaTeX better.) After complaining, comment out
ntheorem stuff at lines 2036 till 2042, right after "SOPHIE TEMPLATE ENDS".
ntheorem has bugs and is outdated and nonmaintained since, I think, 2011. Removing
ntheorem, you will have to deal with the consequence that labeling and referencing theorem-like environments will require more manual work, but this is a better option than failing compilation.
The only alternative I can imagine is that someone repairs