This is a MS Office suite problem.
1.Please use professional and higher versions of Office. Do not use home version.
2.Please make sure that MS Office suite is installed fully.
If above 2 points are not the causes, please try to re-install Office to see if this issue can be solved.
If re-install Office cannot solve this problem, it may be caused by the Add-Ins in local Word.
1. Please open the local Word. Go to File --Options, and click Add-Ins in Word Options.
2. Click Go to Manage COM Add-ins, and Remove all Add-Ins except Aceoffix to see if this issue can be solved.
3. If it's solved, please add the necessary add-ins back one by one to check which add-in causes this issue.
There is another case.
When your scaling on any monitor hooked to the work station is greater than 100%, and using office 365, it will result in Aceoffix opening in Word rather than in Acebrowser.
We had this scaling issue in V5.6 and earlier versions. And our latest version has fixed it.
If you are under this situation, please make the monitor scaling as 100% or update to the latest version at both client and server side.