Hi Erica. I'm Greg, 10 years awarded Windows MVP, specializing in Installation, Performance, Troubleshooting and Activation, here to help you.
A splitter won't extend, only duplicate. It's splitting the same image.
1) Here are tips for setting up multiple monitors in Windows 10 and 11:
https://www.lifewire.com/connect-3-monitors-to-...
https://www.techwalla.com/articles/hook-up-moni...
https://superuser.com/questions/1268348/how-to-...
https://www.drivereasy.com/knowledge/fix-third-...
https://www.pcworld.com/article/427549/how-to-c...
https://www.eizoglobal.com/support/compatibilit...
https://www.addictivetips.com/windows-tips/mult...
https://www.laptopmag.com/how-to/connect-multip...
https://www.youtube.com/watch?v=DhWmTAEAoss
2) Update the Display driver from the PC or motherboard maker's Support Downloads web page for your full model number, HP Serial Number or Dell Service Tag - from the sticker on the PC.
While there check also for newer chipset, BIOS/UEFI firmware (very important), network, sound, USB3 and other drivers, comparing to the ones presently installed in Device Manager reached by right clicking the Start Menu.
If this doesn't give you the latest or ideal driver for what you need, compare it to the driver offered by the Intel driver update Utility here:
http://www.intel.com/content/www/us/en/support/...
or the Nvidia Update utility here:
http://www.nvidia.com/Download/Scan.aspx?lang=e...
or the AMD autodect utility here:
http://support.amd.com/us/gpudownload/windows/P...
For Display issues one fix that is working is to Roll back or Uninstall the Driver on the Display Device > Driver tab, restart PC to reinstall driver.
You can also try older drivers in Device Manager > Display device > Driver tab > Update Driver > Browse > Let Me Pick.
Then you will know you've tried everything in addition to Windows Update drivers, which are rarely enough.
Feel free to ask back any questions. Based on the results you post back I may have other suggestions if necessary.
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