"Unable to switch to Coherence" after upgrading to version 8

F

flakshack

Member
After upgrading to version 8, I am unable to get my main Windows 7 x64 VM to switch to Coherence. I normally run in Coherence all of the time.

I see the message:

Unable to switch to Coherence

The virtual machine display configuration could not be applied. Please try again or contact the Parallels support team for assistance.


I've tried:

Restarting Windows
Removing and reinstalling the Parallels Tools
Enabling/Disabling "Retina Display: Enable full resolution"
Enabling/Disabling 3D acceleration

Restarting OS X fixes the problem, but it eventually starts happening again.

I'm running on a Early 2011 MacBook Pro with a 27" Cinema Display. Parallels Build 8.0.18101
 
Thanks for the replies.

I followed the directions in the second article but no luck.

I should mention that I do not use multiple monitors at the same time. When I connect my MacBook to my cinema display, the MacBook is closed.
 
Last edited:
This might be a necro, but this is the top listing when searching for "Unable to switch to coherence mode parallels 8" so it's the most likely at the time of this posting to get noticed by people having this issue.

After a lot of trial and error, this seems to be an issue with changing hardware profiles. Since I am on a MacBook using Thunderbolt -> DVI connectors on multiple monitors (laptop + 2 Dell flat screens) if I disconnect the monitors to go mobile, the hardware profile instantly changes. Something gets hosed up in the hardware settings of the VM software if parallels is in Coherence mode when I shut down or remove the adaptors.

2 ways to fix this:

#1 Exit Coherence going to normal "screened" mode before unplugging the monitors or powering down
#2 If you forget to do this, after you have received this error; unplug all your monitors, attempt to switch to Coherence while on the laptop screen only, it will fail, but that's OK (this seems to force Parallels to recognize there's been a hardware change). Plug your monitors back in, attempt Coherence mode again, it SHOULD work.

Note that just powering off the monitors doesn't seem to work, I need to actually unplug my T-Bolt adaptors from the laptop in this process.

I have been able to repeat this process to fix the problem several times in a row, as well as intentionally cause the issue by unplugging the monitors.
 
Loadnabox said:
This might be a necro, but this is the top listing when searching for "Unable to switch to coherence mode parallels 8" so it's the most likely at the time of this posting to get noticed by people having this issue.

After a lot of trial and error, this seems to be an issue with changing hardware profiles. Since I am on a MacBook using Thunderbolt -> DVI connectors on multiple monitors (laptop + 2 Dell flat screens) if I disconnect the monitors to go mobile, the hardware profile instantly changes. Something gets hosed up in the hardware settings of the VM software if parallels is in Coherence mode when I shut down or remove the adaptors.

2 ways to fix this:

#1 Exit Coherence going to normal "screened" mode before unplugging the monitors or powering down
#2 If you forget to do this, after you have received this error; unplug all your monitors, attempt to switch to Coherence while on the laptop screen only, it will fail, but that's OK (this seems to force Parallels to recognize there's been a hardware change). Plug your monitors back in, attempt Coherence mode again, it SHOULD work.

Note that just powering off the monitors doesn't seem to work, I need to actually unplug my T-Bolt adaptors from the laptop in this process.

I have been able to repeat this process to fix the problem several times in a row, as well as intentionally cause the issue by unplugging the monitors.
Click to expand...

I too am running a Windows 7 x64 SP 1 build on Parallels 8.

After messing around with this for about 45 minutes I have determined that it is related to your VM (Other VM works just fine; which is Windows 7 32-bit). If anyone has this problem in the future try the following:

1. Perform a system restore in the guest OS from when everything was previously working (Worked for me)
2. Uninstall Parallels Tools and reboot the VM and reinstall. (Try if system restore will not work)
3. Uninstall Parallels Tools, reboot, uninstall the Display drives from within the VM and install Parallels Tools. (Try if previous two solutions don't work)
 
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