I would recommend to enable tamper protection if you are not sure why you have disabled it.
Follow these steps to enable it.
1. Double-click shield icon to bring up SEP client UI.
2. Click Change Settings > Client management > Configure Settings
3. Switch to the Tamper Protection tab, and either change the action to Log the event only or uncheck the option Protect Symantec security software from being tampered with or shut down.
4. Click OK.
5. After completing task requiring tamper protection to be disabled, restore tamper protection to the previous setting.