Windows 10 Creator Fall update has introduced a security feature that controls access by applications to various Windows folders such as the "My Documents" folder.
Flexor saves Call History to a local file on the PC called "calllog.xml" by default this resides in the "My Documents" folder. If you have updated to Windows 10 Creator Fall update and if the Folder Controlled Access feature is enabled, by default it will prevent Flexor saving the file.
A Flexor warning will appear when a call is saved.
As this is as a result of Windows blocking access to the folder click "No".
To allow Flexor to access the folder open Windows Defender Security Centre and click on Virus & Threat Protection.
Then on the next screen scroll down and click on Allow an app through controlled folder access.
On the next screen click on the "+" icon to Add an allowed app.
Then in the file explorer window that appears, browse your PC's drive to the folder containing the Flexor program files. This is likely to be something like c:\program files(x86)\camrivox\Flexor Manager\2.1.145. Then find and select FlexorManager.exe and click open.
Then exit and restart Flexor to enable the change.
Camrivox development is working on adding this change to a future build if possible.
If you are seeing the Error writing warning message and do not have the Windows Folder Access feature enabled, please check security permissions to the folder and make sure Flexor is added to the whitelist / exception list for your Firewall or Antivirus.
This FAQ covers renaming the calllog.xml file.