Hi.
After connecting the set-top box to the mains or even during a full reboot of the set-top box... the first few seconds of the device booting, you must see the manufacturer's logo on the TV.
If you extract the manufacturer's logo (splash....bin file) to disk and rename it to .BMP, you will also see its appearance. The "splash....bin" file format for Vu+ flashing is a plain BMP file at a predetermined resolution and color depth.
This image should appear after turning on the set-top box or during a full reboot of the set-top box. If you did not manage to flash it, maybe you are doing something wrong, or your Vu+ is a different model than you wrote, i.e. other than Duo2.
EDIT:
It is also possible that older Vu+ devices work differently when flashing. For example, they also need some other flash files when flashing, and not just one "splash...bin" file. I'm not sure. It is quite possible.
In the case of my Vu+ Solo SE V2, this one file "splash...bin" and the "force" file what I sent you in the ZIP file are sufficient. That is that all you need is the "splash...bin" file and the "force" file (for the Solo SE V2, since there is no push button to start the flash process, the flash process must be forced by itself from the USB key). I really don't know. Some older set-top boxes are really strange :).
You can try another way... but... as first, backup all your settings before flashing the original Vu+ firmware to the set-top box. After flashing and restoring the original firmware with the original "splash......bin" file, flash the previous firmware again. And restore all your backed up settings. If it is an OpenATV image (firmware), delete the "splash....bin" file from the USB key, after extracting the archive file from OpenATV !