I have the same problem with thread starter, and I've already tried to solve it by user8916413 and user7405115's posts, but it doesn't solve anything.What is the complete error message?
I tried to login with sysadmin n opened up any form, but it didn't work.
FormsLauncher.class Not Found Error When Attempting to Access Forms in Applications [ID 291698.1]Done this, but still the still got the error.
Load: Class Oracle/Apps/Fnd/Formsclient/Formslauncher.Class Not Found. [ID 373736.1]Not suitable with my condition.
Formslauncher.Class Not Found When Failing Over Using DNS Round Robin Load Balancing [ID 604040.1]
Can't Launch Forms in E-Business when accessed via VPN: Formslauncher Notinited [ID 471120.1]
Deploying Sun JRE (Native Plug-in) for Windows Clients in Oracle E-Business Suite 11i [ID 290807.1]
Deploying Sun JRE (Native Plug-in) for Windows Clients in Oracle E-Business Suite Release 12 [ID 393931.1]Kinda helped.