Recently our team faced an issue where the business rule was not getting triggered on ‘Quick Create’ form even after validating it successfully and activating it on all forms on ‘Opportunity’.
Problem statement:
Business rule was setup for showing/hiding certain fields on the opportunity form based on a field value. Business rule was set to trigger on ‘All Forms’. Validated the rule and activated. However, business rule was not getting triggered on ‘Quick Create’ form but it worked for other ‘Main’ form.

Issue Reason:
Business rule was setup for showing/hiding certain fields on the opportunity form(s) based on a field value. Out of the 10 fields configured to show/hide on the form, one of the fields mentioned in the business rule was missing on the ‘Quick Create’ form and that caused the rule not getting triggered. Usually this can happen if we enable business rule based on the fields on the “Main form” and expect the rule to be triggered on the ‘Quick Create’ form as well. If the ‘Quick Create’ form doesn’t have all the fields added on the business rule, entire business rule logic will not be working. This looks silly, but it can take a lot of effort to debug if you are not aware of this.
Hope this helps!