when a user logs in for the first time or the link is opened in Incognito mode, the image added in the text box (using the markdown) is not showing up 
the image is displaying as if we are not connected to the internet
Hi @Priyanka
Post "Diagnostic Info" from Admin > Troubleshooting.
Post the markdown.
Check the browser developer Network-tab to understand what the browser is doing (or not doing).