It appears to work fine on this forum. What version of NodeBB? What do you mean when you say it disappears? Can you record your screen?
Logo disappeared on mobile edition
the logo above the forum categories shows on Chrome Desktop, but does not show anymore on Chrome for Android (Samsung S8) nor iPhone S5 with Safari. On the mobile phones, the logo is in fact shown, but the blue top bar with the three dashes and the chat icon are on top of it.
Before the logo was shown nicely below the blue top bar, and it seems there is a bug .. On the iPhone you can "pull down" the webpage a bit, then the logo can be seen (but it slides up again). On Android we do not have this pull down feature, so it looks like the logo is not loaded, but it is, just hidden.