On Android phones it's Allow 3rd party applications. Maybe you forget such a setting. I don't see you supplying links to a manual so I'll share this and leave it at that.
Hello,. I am a classic nokia user and using only nokia set since nokia 3310, old school nokia handset. I just bought Nokia 500 few days back. I upgraded its software using Nokia Suit, it installed perfectly without no error, whatsoever and my phone worked perfectly. Then i backup my data to my pc using nokia pc suit. Then a day before i downloaded IM for Nokia Chat on the go V3.14.10 application from Nokia store. It downloaded perfectly without any error but when i tried to enter my details on it, my phone set light gradually go dimmed and i seen vertical lines on my display screen and then i have to restart my phone. Then i uninstalled that cursed application. To prevent any further problem, i hard reset my phone and then reinstalled my software using Nokia PC Suit today, it also installed perfectly. Then i restored my all backup data while using nokia pc suit. but i could not see my customize applications icons which i installed before hard reset. I can see their installation files in installation menu but i cant see their icons on the main menu and i cant use them.then i tried to download again those application from phone using Wifi or using nokia suit which was previously on my handset before hard reset but whenever i try to install those particular applications i got installation failed error. While i can easily download and install those application which was not on my phone before hard reset and before re installing software.What i am doing wrong or what went wrong?