Something else is happening and I'm not sure how to address it with Site Customization?
Is your segment value correct?
For example, a segment set to match exactly "industry" of "Fin-Tech" will most likely not trigger a customization as by default these return standardized ISO values upon site visit. The exception in this case is if you have connected with your Customer Success Manager to customize your return values. More on firmographic attributes here.
Do you have CSS or inline style rules on your site/element that may be conflicting with your customization? Or did your previous element have an inline customization which needs to be added into Site Customization?