The following message appeared when I tried to convert. I tried 1 month ago as well incase it was a temporary issue. I am using Windows Explorer & have installed Active X. "An unexpected problem occurred on the server during your request. You can:
Wait a while and try again. The problem could be temporary and may be resolved in a few minutes.
Modify what you're doing (for example, if you are trying to create a report, customize it to display less data).
If you continue to have problems, contact Support.
I can honestly tell you that the last couple of conversions required me to contact my support team at Intuit for assistance. The program hung and I could not get past a specific step that @VivienJ described below. The support tech had me using an incognito window and he had me change my IE version from 11 to IE9 to get it to finally work. I have also seen that I am not alone on struggling with this task, which should not be as difficult as it is.
I would contact Intuit support and have them help you thru this. They will be more than happy to do so and are aware of this problem. Be prepared that they will need to log in and do the steps and it take some time.
In addition to the resources and guides that @VivienJ included, I wanted to suggest ensuring that the user has the correct accesses. In QuickBooks Online, only three types of users can export, which are the Master Administrator, Company Administrator and Accountant. In the past, I've seen similar error messages when a user with incorrect accesses attempted to export company data. Additionally, if it wasn't the Master Administrator that was initiating the export, I suggest having them try. Should the Master Administrator be unavailable or they were the ones that initiated the export, I suggest trying another Company Administrator. The following article contains additional information on export requirements: Export Data File from QuickBooks Online to Desktop.
As @lynda said, you may wish to consider contacting the Phone Support Team if you continue to experience this behavior when exporting. They have specialized tools, such as screen sharing, to review your account and provide further assistance. Here's how you can reach them:
It has been months since I needed to get a backup of a client's QBO or convert a client to desktop. That said, attempting this yesterday (08/01/18) caused much frustration and ultimately I gave up for the day. In the past, this was a rather SIMPLE task! NOT anymore. Here is what I finally figured out, that NONE of the Intuit dialogue boxes or "help" will tell you.
1. Open your desktop QB in ADMINISTRATOR MODE! (this is KEY and not mentioned ANYWHERE in the QBO instructions as you are creating/downloading/converting the file!).
To do this, right click the QB desktop icon, and click "Run as administrator." If a company file opens, close it so that you are at the main QB screen to choose what company to open.
2. Open Internet Explorer in ADMINISTRATOR MODE! (again, key and not mentioned by Intuit). Do this the same way as above for QB Admin Mode. Also of note, you MUST USE IE for this process. You cannot use ANY other browser. If you do not have IE, go get it.
3. AS SOON AS YOU OPEN Internet Explorer, BEFORE you login to QBO, you MUST turn off your pop-up blocker. Attempting to do this AFTER logging into QBO and while you're in the process of converting will serve only to lock up the QBO website!
To turn off the pop up blocker in IE, go to the tools icon, choose Internet Options. Go to the "Privacy" tab. UN-check "Turn on Pop-up Blocker".
4. Login to your QBO account. Click the gear icon, select "Export Data".
From that point forward, it is pretty self explanatory, and by following the on-screen instructions you should have your desktop backup/working file in no time. It would have saved me HOURS had steps 1 - 3 above been included in the instructions AT the QBO account. Intuit FAIL!