This article explains why logos configured for Salesforce Classic apps may not appear in Lightning Experience. This occurs because Lightning Experience uses a different app framework that does not retain Classic app branding.
To resolve this issue, upgrade the app to a Lightning app and re-upload the logo.
Logos configured for Salesforce Classic applications may be replaced by default images when viewed in Lightning Experience because branding settings are not carried over during the transition.
005239126

We use three kinds of cookies on our websites: required, functional, and advertising. You can choose whether functional and advertising cookies apply. Click on the different cookie categories to find out more about each category and to change the default settings.
Privacy Statement
Required cookies are necessary for basic website functionality. Some examples include: session cookies needed to transmit the website, authentication cookies, and security cookies.
Functional cookies enhance functions, performance, and services on the website. Some examples include: cookies used to analyze site traffic, cookies used for market research, and cookies used to display advertising that is not directed to a particular individual.
Advertising cookies track activity across websites in order to understand a viewer’s interests, and direct them specific marketing. Some examples include: cookies used for remarketing, or interest-based advertising.