Macros keep disappearing

I've created several sheets in ZOHO Sheet all with a number of macros to perform repetitive tasks such as data manipulation and formatting... However, they keep disappearing from the macro list, comes up "No Macros Found" this is happening on several sheets and appears to happen randomly.. its is getting quite annoying to be honest as I'm now having to continually re-enter the macros.. So, in effect I've replaced a set of repetitive tasks with another repetitive task of re-entering the macro !!... Can anyone explain why this could be happening ? And how I can stop it happening ?? Thanks