No Blocked Sites show in Firefox after Immunization

[DocCovington]

Hello folks,

I have noticed something worrisome and would like to know how to resolve this issue: Whenever I immunize my system now, it shows that all Firefox entries have been successfully immunized. However, upon opening Firefox's Options and checking under Privacy & Security > History > Exceptions, none of the many websites supposedly blocked by Spybot's immunization show - the Exceptions list remains empty.

I am using Firefox 56.0.2 and Spybot 2.6.46.0.

Does anybody happen to know what the problem might be?

Thanks in advance for any helpful insight,
Doc