In the Logs workspace of your Azure Function, if custom logs are absent, check these most likely culprits: There are a few possible explanations for this:

Logging Configuration: Make sure that logging is configured in the Azure Function App that you are using. Use the Azure portal settings to verify that Application Insights has been set.

Log Levels: Ensure that your function code invokes logs at the right log levels. If Node.js is your choice, for example, console.log() should be used at the Information level or higher. In Python, make use of print() statements as needed.

Diagnostic Settings: Find out if you have turned on diagnostic settings for your Function App. In the absence of these settings, logs are unlikely to be transmitted to the Log Analytics workspace. They can indeed be activated in Azure portal under the “Monitoring” tab of your Function App.

Application Insights Integration: You need to confirm that your Function App has been integrated with Application Insights. Lack of or an erroneous instrumentation key or connection string means the log may not be transmitted to Application Insights and hence not show in the Logs workspace.