How to solve this?
WARNING: The vboxdrv kernel module is not loaded. Either there is no module
available for the current kernel (7.1.9-1-MANJARO) or it failed to
load. Please recompile the kernel module and install it by
sudo /sbin/vboxconfig
You will not be able to start VMs until this problem is fixed.
/usr/lib/virtualbox/VirtualBox: symbol lookup error: /usr/lib/libQt6Help.so.6: undefined symbol: _ZN14QObjectPrivateC2E16QtPrivate_6_11_2, version Qt_6_PRIVATE_API
Welcome to the forum! 
sudo pacman -S linux-virtualbox-host-modules-meta
Kernel 7.1 has reached EOL and is no longer supported or updated.
It is generally recommended to use an LTS kernel – Kernel 6.18 (LTS) is a proven option; or consider Kernel 7.2 if your hardware is very new.
On Arch/Manjaro, the actual command is, as far as I recall:
sudo vboxreload
… assuming you have the necessary modules installed. This may need to be done for each kernel you wish to run.
In case these may be found useful:
VBoxManage Command Reference:
Thanks for the tips
Further thoughts: if you are using e.g. mhwd-kernel -i linux72 this should pull in the headers for VirtualBox, etc. for you. This doesn’t happen if installing a Kernel via pacman directly; you have to tag on the modules to the command yourself (or add them afterwards). 
It’s now working, thanks!
Could you let us know what you actually did to get it working?
Also it’s usual procedure to mark the most appropriate post as a Solution, which helps others with the same issue to find it.