I had the exact same issue yesterday with a custom frontend theme after updating from 2.3.1 to 2.3.4. I fixed the issue by changing the settings in Content/Design/Configuration. I added the same theme to the 3 options on the last column "Theme Name". Before that, I only had the last line "Default Store View" pointing the custom theme. The first lines "Global" and "Main Website" were blank, with no theme selected. Assigning the same themethemes to the 3 options fixed the issue.
I had the exact same issue yesterday with a custom frontend theme after updating from 2.3.1 to 2.3.4. I fixed the issue by changing the settings in Content/Design/Configuration. I added the same theme to the 3 options on the last column "Theme Name". Before that, I only had the last line "Default Store View" pointing the custom theme. The first lines "Global" and "Main Website" were blank, with no theme selected. Assigning the same theme to the 3 options fixed the issue.
I had the exact same issue yesterday with a custom frontend theme after updating from 2.3.1 to 2.3.4. I fixed the issue by changing the settings in Content/Design/Configuration. I only had the last line "Default Store View" pointing the custom theme. The first lines "Global" and "Main Website" were blank, with no theme selected. Assigning themes to the 3 options fixed the issue.
I had the exact same issue yesterday with a custom frontend theme after updating from 2.3.1 to 2.3.4. I fixed the issue by changing the settings in Content/Design/Configuration. I added the same theme to the 3 options on the last column "Theme Name". Before that, I only had the last line "Default Store View" pointing the custom theme. The first lines "Global" and "Main Website" were blank, with no theme selected. Assigning the same theme to the 3 options fixed the issue.