Problems updating Travelify theme - customizations are lost

When updating our theme from version 1.5.0 to 2.4.1, we lose much of our custom styling (e.g., green background in navigation menu instead of purple). We use the following plugin to enter any CSS style changes and have not directly edited the CSS style sheet: Simple Custom CSS plugin.
Thanks in advance for your help.

Hi Mary,

I hope you are well today and thanks for posting here.

Do you mean the custom styling code saved in the Simple Custom CSS plugin option got lost after updating Travelify theme or anything else?

Please advise and also share your site URL so that i can test it.

Kind Regards,