Not possible to extend print selection

Hello,

I'm new here and have a question. Since a week or two i can't pull down my blue line which represents the printselection. Normally i always went with my mouse to the blue line and pulled it down to get more cells to work in. This is not working anymore. I send the file to a friend and when he opens it it works perfectly. Does anyone know what is the problem with my Excel? Hope someone can help me. I have Office 2019!