Register button not visible in portal

[KafilBaig]

I am trying to add webappbuilder in Portal for ArcGIS 10.6.1 from the content - add item - add application 

the register button is not visible . 

If my portal n webappbuilder is on same server the register button will not visible is it??

as per the research got the below info 

Note:
The Register option is not available if the app is hosted on the same web server as the portal's web adaptor. For instructions on how to register these apps, see Esri technical article 44907.

should we run the webappbuilder in different machine than the Portal for ArcGIS hosted machine . 

[RoberthSanchez]

Kafil, what you mean is that you have a server with ArcGIS Server - ArcGIS Web adaptor and Portal for ArcGIS but you have a stand-alone versión of Web appbuilder  hosted there too? i'm asking because Portal for ArcGIS Comes with a versión of Web appbuilder inside that is used to make hosted apps in portal.

[KafilBaig]

Yes we have a windows 2016 server for

Arcgis for Server 10.6.1

Portal for ArcGIS 10.6.1

Arcgis Webadaptor

Webappbuilder 2.11 stand alone hosted on same machine .

Sent from my iPhone

[RoberthSanchez]

Why do you want to share WebAppBuilder 2.11 Stand alone? you can add custom widgets in portal since version 10.5.1 remenber that ArcGIS Web appbuilder stand alone is for developers (always installing on developer clients), if you want to deploy an app created with web appbuilder you must download it and make the deploy on some web server (By example IIS):

https://doc.arcgis.com/es/web-appbuilder/manage-apps/deploy-app.htm

Or in the case of a widget, download it and share it to portal ussing the custom widget option, you can't expose your web appbuilder stand alone version trough portal because is a internal link (is not hosted and exposed to the public by a web server).

I hope this can be usefull for you.

Regards.