In C++, capitalisation matters. Your post suggests you’ve used
Declare_Log_Category_Extern(MyLog, Log, All);
Instead of
DECLARE_LOG_CATEGORY_EXTERN(MyLog, Log, All);
And
Define_Log_Category(MyLog);
Instead of
DEFINE_LOG_CATEGORY(MyLog);
Update to use capitals and see if that fixes the issue.
Also, My DEFINE_LOG_CATEGORY are in .cpp and DECLATE_LOG_CATEGORY_EXTERN is in .h