iOS:
To make a debug log, you would need to do the following:
1) Run Zoiper;
2) Go to Settings -> Advanced and enable the "Debug log" option;
3) Replicate the issue;
4) Disable the "Debug log" option.
Afterwards pull-out the debug log file following these steps:
1) Sync the device with iTunes;
2) Open the device in iTunes and go to the "Apps" section;
3) Scroll down to File sharing and select Zoiper;
4) On the right you should see a file called zoiper-log.txt, store it onto your computer by using the "Save to" button.
5) Send the file to us.
How to get crash logs/dumps from iOS
Please connect the device to your computer and sync it with iTunes. Now go in Finder to following folder
In Finder hit "Shift + CMD + G" and type `~/Library/Logs/CrashReporter/MobileDevice` (or Go to "Library" by clicking the "Go" menu while holding the ALT key down and then navigate to `Logs/CrashReporter/MobileDevice`)
`<YOUR HOME FOLDER>/Library/Logs/CrashReporter/MobileDevice/<YOUR DEVICE NAME>`
- Mac OS X: `~/Library/Logs/CrashReporter/MobileDevice/<Device name>` folder
- Windows XP: `C:\Documents and Settings\\Application Data\Apple computer\Logs\CrashReporter\<Device name>`
- Windows 7/8: `C:\Users\AppData\Roaming\Apple computer\Logs\CrashReporter\MobileDevice\<Device name>`
and look for files named like this
Zoiper_ ... .crash
Zoiper_ ... .plist
If there are such files, please send them to us.
You can retrieve crash reports from an iOS device and send them to us via email by following these instructions.
Please keep in mind that these Crash Reports are not enough when our team has requested log files. Please refer to the above two sections instead - namely "Debug Log" and "crash logs/dumps from iOS"
(It is not possible to get device console logs directly from a device)
1) Open Settings app
2) Go to Privacy, then Analytics
3) Select Analytics Data
4) Locate the log for Zoiper. The logs will be named in the format: <AppName>_<DateTime>_<DeviceName>
5) Select the desired log.
5.1) Tap the share button on the top right corner, then send the file to us via email.
5.2) Or you can: using the text selection UI select the entire text of the log. Once the text is selected, tap Copy
5.3) Paste the copied text to Mail and send to an email address as desired
Source - https://developer.apple.com/library/archive/qa/qa1747/_index.html
Android:
What is the most requested log file?
For troubleshooting purposes, our team would usually request a debug log file.
A Debug log would help us to observe the sequence of events that took place.
Debug log
First, you will need to enable the debug logger.
Run your Zoiper for Android and dial 
7827833284 in order to enable Diagnostics menu.
Then open Config -> Diagnostic -> Debug log -> and select Enable debug log.
Now try to recreate the issue.
Then go to back to Config -> Diagnostic -> Debug log and click "Send debug log".
Your mail client will start, ready to forward the debug log.
Change the recipient email to android @ zoiper . com
Later, when you do not need the log file, use "Delete debug log file" to remove it.
Note:The debug logger will be active until the next restart of Zoiper.
Packet capture log
A Packet Capture could show what packets were sent and received by the softphone at the time when the issue occurred.
Android does not have a built-in tool for creating packet captures. You could try using some of the tools available in GooglePlaystore, yet it might not work as expected on your device.
Verbose Logs
To do so, please follow the steps below:
Unlock "Diagnostics" - as shown in the beginning of this guide.
Select "start verbose logging"
Reproduce the issue (exit Zoiper, start it again). Then go to "Diagnostics" and select "send logcat" then notify us via email so we can check it.
Let us know what email address you used to send the log and what is the exact model of your phone.
Other required information
We would need to know the exact version of Android running on the device. Is it a custom or a stock ROM?
To obtain this information, go to Android settings -> About Phone -> Software information;
Send us the information shown in the Zoiper About screen: *
Zoiper -> Config -> About ->
- The current Zoiper version that is running on your device;
- the library revision number;
- Manufacturer;
- Brand;
- Model;
* This information may look the same as the one taken from the About phone section.