Hi,
Please try the below troubleshooting methods and check if you can find the options to pin to taskbar.
Method 1.
You can run the Windows store apps troubleshooter on Windows 10. Follow the below steps to perform System maintenance troubleshooter.
1. Press Windows + X keys on the keyboard and select Control Panel
2. Type Troubleshooting in the search bar on the Control Panel.
3. Click on View all on the left navigation pane.
4. Click on Windows store apps.
5. Click on Advanced on the Windows store apps dialog box and click on Run as administrator (Enter the credentials
if required).
6. Click on Next and follow onscreen instruction complete the Windows store apps troubleshooter.
If the issue still persist try this method.
Method 2.
This issue could be due to the system file is corrupt. I recommend you to perform SFC scan, System File Checker is a utility in Windows that allows users to scan for corruptions in Windows system files and restore corrupted files.
Follow the below link on how to run SFC scan.
http://answers.microsoft.com/en-us/windows/wiki/windows_10-update/system-file-check-sfc-scan-and-repair-system-files/bc609315-da1f-4775-812c-695b60477a93
If the issue still persist, I suggest you to
install all Windows as well as optional updates on the system. Windows Update
helps keep your computer up to date with the latest system updates and drivers.
You can check Windows Update manually to help ensure you have the latest updates by following the below steps:
1. Go to Start and then
Settings.
2. Click on Update and Recovery.
3. Check for updates under
Windows Updates.
4. Restart the system and check if the issue is resolved.
Keep us updated if you could pin the applications to taskbar.