outlook-2013-signature-button-in-options-does-not-open

After installing Outlook’s January 2018 update, some users are unable to edit signatures.
Microsoft has identified the cause as having both the Windows app store version installed as well as a “normal” version. This would be the case if you have a new computer and Office was preinstalled, then you installed your own copy of Office.
After uninstalling the Windows store app the Stationery button should work.

1. Open Settings, Find Apps & features.
2. Click on the Office Desktop App and select Uninstall
   
3. A second small Uninstall dialog will open, for you to confirm.
   

Stationery and Fonts button is grayed out
This is the original cause of the buttons not working and dates back to 2012.
A fairly common problem for 64-bit Windows users is that Outlook’s Stationery and Fonts or Signatures buttons won’t work.
When the Stationery and Fonts or the Signatures button is grayed out or won’t do anything when you click it, you may need to edit the registry.

First, empty your Temporary Internet Files. This may or may not help much, but even if it doesn’t do any good, your Internet cache will be clean.
Empty your temp internet files and if it still fails, change both (Default) and LocalServer32 values in each of the following keys to the appropriate path for your installation of Outlook.

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Wow6432Node\CLSID\{0006F03A-0000-0000-C000-000000000046}\LocalServer32

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{0006F03A-0000-0000-C000-000000000046}\LocalServer32

Default installation paths for Office / Outlook are:
Outlook 2016 Subscriptions & Retail Licenses 64-bit:

C:\Program Files\Microsoft Office 16\root\office16\Outlook.exe

Outlook 2016 Subscriptions & Retail Licenses 32-bit:

C:\Program Files (x86)\Microsoft Office 16\root\office16\Outlook.exe

Outlook 2016 ProPlus (volume license) 64-bit:

C:\Program Files\Microsoft Office\Office16\Outlook.exe

Outlook 2016 ProPlus (volume license) 32-bit:

C:\Program Files (x86)\Microsoft Office\Office16\Outlook.exe

Outlook 2013 Subscriptions & Retail Licenses 64-bit:

C:\Program Files\Microsoft Office 15\root\office15\Outlook.exe

Outlook 2013 Subscriptions & Retail Licenses 32-bit:

C:\Program Files (x86)\Microsoft Office 15\root\office15\Outlook.exe

Outlook 2013 ProPlus (volume license) 64-bit:

C:\Program Files\Microsoft Office\Office15\Outlook.exe

Outlook 2013 ProPlus (volume license) 32-bit:

C:\Program Files (x86)\Microsoft Office\Office15\Outlook.exe

Outlook 2010:

C:\Program Files (x86)\Microsoft Office\Office14\Outlook.exe

Don’t forget to restart Outlook after editing the registry.