External monitor problem iMac 2017 High Sierra.

Having a mac pro, there is no alternative except an external monitor.

Since the beginning if I unplug the monitor, then turn it back on, it works. Turning on and off on the remote doesnt do it.

I bought a smart plug so I can do this via Alexa, which isnt perfect but at least is easier. Wonder if anyone else finds that unplugging helps

This worked for myself as well. Note: I'm using the VanTech USB 3.0 To HDMI Adapter. It uses the display link driver, but the official download on vantech is v2.5.1 while the display link driver is v4+.

My Samsung U28E510 is still recognized but is out of whack. The mouse cursor is in a different position than the system thinks it is as if the resolution scaling is messed up... The cursor only shows up in a box that takes up about 80% of the screen, and won't go past that. If I close the lid on my MB Pro and then figure out how to correct for the messed up positioning of the mouse, if I then manage to click on a scaled resolution change, it works, but if I open the lid, things get out whack again.

When connecting Satechi or similar USB-C -> HDMI adapter most of the time Mac will completely freeze (15 inch MacBook Pro mid-2017).

After testing bit of testing, problem seems to be solved using any USB-C -> Displayport/mDVI/DVI cable or adapter. I used new DELL U-series monitor.

Apple, we are waiting for a fix!

Appreciate your reply yousseff - thank you.

I tried the Display Installer 4.1.11 that you suggested. Unfortunately - still no go.

From what I have read, it seems as though many people are experiencing this 'Thunderbolt connection problem' - since the installation of Mac OS High Sierra. I hope that Apple techs. are working on a fix for this problem ?

Funny thing is - If I detach the Thunderbolt adapter & then plug the HDMI cable (to my television) directly into my Mac's HDMI port, the signal is transferred to my television successfully ! Therefore, I'm thinking of purchasing a good quality HDMI 'powered' splitter to enable my computer monitor & television to work together again.

Thanks again for your help

Sure - here's the one I purchased. I ordered it on Saturday and arrived on Monday. RatsSmart Mini Displayport to HDMI 6 FT Thunderbolt to HDMI Adapter, it was $6.99 new on Ebay. I like how this one single cord as opposed to having a adapter connected to your HDMI cable. Again though my Apple adapter I have been using for 6-7 years so it was time.

Mini Displayport to HDMI 6 FT Thunderbolt to HDMI Adapter for Apple Macbook | eBay

ALSO - my bad my MBP 2011 has a Thunderbolt port not a DVI port that was a mistake on my earlier post.

I would also make sure you have checked all the suggestions in this post before ordering a new cable, especially resetting the system management controller.

1. Shut down the Mac and connect it to your MagSafe adapter and a wall outlet as usual.
2. Hold down the Shift+Control+Option+Power button at the same time for a few seconds.
3. Release all keys at the same time, then boot the Mac as usual.

Good luck,

JB

I had the same issue and quick fix was to revert older version of osx on my iMac. What a pain! This was only solution at the time and could not live without xtrnal display for my mac book pro.

Themacmommy-

YES! I used that driver with a wavlink and my monitor now works. I think it is worth a shot even if it doesnt fix your problem!

Try adjusting your resolution?

I think the key here is the Thunderbolt 3 to DisplayPort 4K. As I said, certainly for me nothing else has worked. My new secondary screen shows 4K and everything works. Finally.