First, ensure that you turned them on:
If this does not help, ensure that the following registry key contains no more than 15 icons (this is the limit posed by Windows):
HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Windows\ _ CurrentVersion\explorer\ShellIconOverlayIdentifiers
Quoting the TortoiseSVN team:
After installing the 32-bit (x86) "2015 C runtime" TortoiseSVN icon overlays will be shown in XYplorer again.