If the Lock the taskbar option is grayed out under Taskbar and Start Menu Properties, a registry change can solve the issue.

1. Hold down the Windows key and press R (Or click Start > Run).

2. Type regedit and click OK.

3. Click the plus sign next to HKEY_CURRENT_USER
then Software
then Microsoft
then Windows
then CurrentVersion
then Policies
then click Explorer

4. Look for an entry on the right side for LockTaskBar. Right-click the entry and Delete it.