Hy guys, we have to schedule a QRadar upgrade from 7.4.3 to 7.5.
Reading the prerequisites checklist, one point is the following one:

Resolve any issues with applications in an error state or not displaying properly.


Recently, our installed apps are showing us a blank page, all of them. This kind of problem can be fixed by the update or can negatively impact it?

For the beginning: Did you try to restart them using /opt/qradar/qappmanager ? Did you see any messages under the alerts (top right) that relate to certificates ? 

When it comes to apps certicate related issues are often seen as the cause. 

Hi Dusan, going in ssh on my QRadar Console VM and reaching path /opt/qradar I cannot see no file, script and/or directory named qappmanager.

About your second question, I have no alerts/warning about certificates.

Sorry, I mistyped - proper path to the tool is /opt/qradar/support/qappmanager .
There are few more details about it provided here: QRadar: About the qappmanager support utility .