Contribution Confirmation Page Issue in Joomla after upgrade
After a long search and resetting paths and clearing cache and checking the .setting files 100s of times the issue was not with the site URL vs the .setting URLS being different aliases as pointed by many of the answers found; it was a damn malware!! 3 sites with the same phishing link in the defines.php in the includes folder. Who would have guessed that. Ths submissions were attempted to be redirected and civi pushes it back to the home page.
As always curse the virus and malware creators!!