When i upload and submit my work sometimes leter preview will dessapered.
On PC also.
Probably a browser problem. Try viewing with another browser.
Do the usual things: Clear cache, cookies and browser history, logout/login, browse in private settings, use a different browser, use a different device, use a different network.
One of those should solve the problem. If a different device helps, check the firewall settings. If a different network helps, check the router's firewall settings.