Could it be that the 2nd screen isn’t as compatible as you believed? Either that, or perhaps it’s faulty.
In any case, some housekeeping:
Welcome to the Manjaro community.
As a new forum user, please take some time to familiarise yourself with Forum requirements; in particular, the many ways to use the forum to your benefit:
Required Reading:
Update Announcements:
The Update Announcements contain update related information and a Known Issues and Solutions section that should generally be checked before posting a request for support.
System Information:
Output of the following command (formatted according to forum requirements) may be useful for those wishing to help:
inxi --admin --verbosity=8 --filter --no-host --width
Be prepared to provide more information and outputs from other commands when asked.
Regards.