The solution is very simple!
Be sure what the depency the browser have. If the browser an 64bit based browser, be sure that the registry entry is set:
Chrome (32bit): KEY_LOCAL_MACHINE\SOFTWARE\Google\Chrome\Extensions
Chrome (64bit): KEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Google\Chrome\Extensions
Firefox (32bit): KEY_LOCAL_MACHINE\SOFTWARE\MozillaPlugins
Firefox (64bit): KEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\MozillaPlugins
Here is a little .reg script:
Windows Registry Editor Version 5.00
; MOZILLA 32bit
[HKEY_LOCAL_MACHINE\SOFTWARE\MozillaPlugins\@worpg.de/npworpg,version=1.0.0]
"Description"="World of RPG Browser Plugin"
"Path"="C:\\Program Files (x86)\\World of RPG\\plugins\\npworpg.dll"
"ProductName"="npworpg"
"Vendor"="World of RPG"
"Version"="1.0.0"
[HKEY_LOCAL_MACHINE\SOFTWARE\MozillaPlugins\@worpg.de/WoRPG,version=1.0.0\MimeTypes]
[HKEY_LOCAL_MACHINE\SOFTWARE\MozillaPlugins\@worpg.de/WoRPG,version=1.0.0\MimeTypes\application/x-worpg-launcher]
"Description"="World of RPG"
; MOZILLA 64bit
[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\MozillaPlugins\@worpg.de/npworpg,version=1.0.0]
"Description"="World of RPG Browser Plugin"
"Path"="C:\\Program Files (x86)\\World of RPG\\plugins\\npworpg.dll"
"ProductName"="npworpg"
"Vendor"="World of RPG"
"Version"="1.0.0"
[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\MozillaPlugins\@worpg.de/WoRPG,version=1.0.0\MimeTypes]
[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\MozillaPlugins\@worpg.de/WoRPG,version=1.0.0\MimeTypes\application/x-worpg-launcher]
"Description"="World of RPG"
; CHROME 32bit
[HKEY_LOCAL_MACHINE\SOFTWARE\Google\Chrome\Extensions\ckpknilfoflolaglllnonhhhnfhaidom]
"Path"="C:\\Program Files (x86)\\World of RPG\\plugins\\npworpg.dll"
"Version"="1.0.0"
; CHROME 64bit
[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Google\Chrome\Extensions\ckpknilfoflolaglllnonhhhnfhaidom]
"Path"="C:\\Program Files (x86)\\World of RPG\\plugins\\npworpg.dll"
"Version"="1.0.0"