A diary code may not work for various reasons. First, double-check if you have entered the diary code correctly.
Maximum number of co-writers reached
For security reasons, there is a maximum limit on the number of co-writers allowed. If all the available codes are already in use, the code will not work.
Diary not yet created
It's possible that you received a diary code, but the main writer (patient or their legal representative) has not yet created the diary. To be sure, contact the diary administrator.