Thanks for reaching out.
In reference to your question here, please navigate to the Appearance>Customize>General Options>Header and enable the “sticky header” option.
I hope this helps.
I am afraid I do not see it…
find attached screenshot
well, It seems it got fixed. I updated the theme and it resolved.
I’m glad that you have managed to have the issue resolved.
Please feel free to reach out once again in case of any more questions.