Activate Solution is Disabled (greyed out) in Site collection Solution gallery

Issue :

User want to save subsite as template to use it to create many subsites with same structure.

Able to save subsite as a template with below direct link ..

Since the site template is disabled in the Publishing sites the option Save Site as Template is not available in the Site Settings you will need to navigate to the page directly: http://yourdomain.sharepoint.com/_layouts/savetmpl.aspx

Once create templet, tried to create site with new custom template but its not showing in Custom section:

When tried to check current status of saved templet file into solution gallery :

Ideally it should be in activated state.

But it was not activated & even if we select solution & tried to activated it, those options of ribbon was disable (greyed out)!

Cause:

The options are in Disabled mode because the required services on server is not activated on farm level in SP2016 farm.

To check if the service is running do the following:

Open the Central Administration
Go to Application Management -> Manage Services on Server
Make sure that the Microsoft SharePoint Foundation Sandbox Code Service is running

Resolution :

Enable Sandbox solutions on SharePoint 2016

To start the service, go to System Settings -> Manage Services in this Farm
Locate Microsoft SharePoint Foundation Sandboxed Code Service and Enable Auto Provision
Locate Microsoft SharePoint Foundation Sandboxed Code Service and Enable Auto Provision

If the provision fails open the console SharePoint Management Shell and execute this command on WFE servers only.

Get-SPServiceInstance -server $env:COMPUTERNAME | where-object {$_.TypeName -eq "Microsoft SharePoint Foundation Sandboxed Code Service"} | Start-SPServiceInstance -confirm:$false > $null

In your server open the services window and check if the SharePoint User Code Host is in running state.