Even though group policy is not installed, it does not prevent restrictions and policies from being placed on your computer. Some malware will add policies on your machine to restrict some windows tools to make it difficult to remove.
If you feel this is the case, the restriction may not have been added through gpedit.msc but instead added directly in the registry.
1. Please copy and paste the text between the cut lines into notepad.
2. Save the file as FIX_SRPOLICY.REG.
3. Double Click on the FIX_SRPOLICY.REG and confirm adding to registry
4. Attempt to access system restore again, please let us know the results
-----CUT-----------
REGEDIT4
[HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\Windows NT\SystemRestore]
"DisableConfig"=-
"DisableSR"=-
-----CUT-----------
This will require a reboot before the changes take effect. Afterwards you should have access to system restore IF it was caused by policies placed on the machine.