ctrl+m used to work as collapse/uncollapse shortcut before I installed vsvim. After installing vsvim using the zo command is uncollapsing a C# region block. But do not have a shortcut to fold till the end of the region. Using zf/string folds incorrectly. There should be a better shortcut.
I have reassigned the ctrm+m to be used. This could be done using the Options button shown at the bottom of the editor. This solved my issue.