Hi @Alba Ampar, Thanks for reaching out here. I ran a search and stumbled upon this thread that might help. Please keep us posted as you make progress. 

Hi @Alba Ampar ! Welcome to the Amplitude Community 

Hm, this is an interesting one because you do have events coming into Amplitude. This means that there isn’t an issue with the JS SDK and events are not blocked/deleted. 

My next theory would be adblocker or some sort of browser extension that would block the events from a specific user to come through but you mentioned “events from other users created in the same test case and in the same conditions are logged” and “all the ads or track blockers are turned off”.

Is it maybe possible that the events went to the wrong Project? You should be able to see the API key listed in the console! 

Hi @belinda.chiu! 
Thank you for your reply! Unfortunatelly, no, events are not logged to any other project either.
What bother us most is that even meta data is not displayed in Amplitude. It usually the case with ads and track blockers, but in the case above it’s not :( 

Thanks @Alba Ampar ! Did you happen to notice anything different between “events from other users created in the same test case and in the same conditions are logged” vs this particular user that didn’t have data in Amplitude? Do you also happen to have the payload saved for the event?

Also do you use our JS SDK directly or do you use Segment etc to send data to Amplitude? 

> Did you happen to notice anything different between “events from other users created in the same test case and in the same conditions are logged” vs this particular user that didn’t have data in Amplitude

nope, it looks random, we tested for a few days and did not manage to get any difference between users that had events displayed and those who did not. 

> Also do you use our JS SDK directly or do you use Segment etc to send data to Amplitude? 

Directly 

> Do you also happen to have the payload saved for the event?

Unfortunately, I do not have for that example from the screen, but here’s a payload for the one not logged today:

1. checksum: cd3898d8954c190d900d4f2912a249f2

2. client: 971517cf6bcbadcfd3f4ddef19dc4ebc

3. e: c{"device_id":"bMMYkN4SfI1-y3Av9WXBIG","user_id":"30067727","timestamp":1648831613181,"event_id":82,"session_id":1648831559713,"event_type":"WAPhoneChosen","version_name":null,"platform":"Web","os_name":"Chrome","os_version":"99","device_model":"Mac OS","device_manufacturer":null,"language":"ru","api_properties":{},"event_properties":{"type":"iOS"},"user_properties":{},"uuid":"47b51b80-3e20-4e8d-9783-e8f5e1db9faa","library":{"name":"amplitude-js","version":"8.16.1"},"sequence_number":96,"groups":{},"group_properties":{},"user_agent":"Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/99.0.4844.84 Safari/537.36"}]

4. upload_time: 1648831613182

5. v: 2

Hi @Alba Ampar ! I have asked the Community Manager to help transfer this to a Support ticket as we have crossed out the main suspects for a missing event from specific users. We’ll continue the conversation through the ticket and raise a case to Engineering if we need further support! 

Just to close out this Community post, after a bit more debugging, we found it’s because a different API key was being used on the events thus sending the events to a different project! Events were not lost, just in a project that was unexpected.