@jy-ping.Y.Ping Hi, thank you for your response & advice! Switching to chrome from safari worked for me after clearing my cache. Thank you so much helping to troubleshoot this!

By buttons do you mean the icons like the stars on the tab side? The star symbols have disappeared on my screen under the syllabus section but the space of where it should be is still there & I can still watch lessons, I just can't mark lessons I want to come back to. I noticed this disappeared about 1 1/2- 2 hours ago.