Command Bar disappears when editing in List / SP Modern

[Jackievo]

hi everyone, 

Since weeks, we've encountered a problem when the Command bar in List disappears while editing. 

It looks fine when I start editing, but when the texts is long than one page, the Command bar just disappears, that mean I won't be able to save whatever I've been editing. Any idea how to fix this problem please? 

1st screenshot: when start editing 

2nd screenshot: after filling in the page with text, the command bar disappears 

Thank you so much 

Jacqueline 

[#2]

Have you tried to change your browser?
What is the SharePoint version?

[#3]

@Alireza Rahimifarid Yes, I have. The standard one was Internet Explorer before, recently we have switched to Chrome. I also thought that one of the browsers could be the cause of this strange behavior but the Command Bar was no where to be seen in both Browsers. We are using SP Modern. 

Thanks for trying to help @Alireza Rahimifarid  appreciate it! 

Kind regards, 

Jacqueline