You can try clicking on the gear icon to the right and selecting the middle option “look up”. It may or may not fill in the data on CE3FZL depending upon whether that DX info is in the data base you selected at setup. Either way, it will not affect your log when you submit it. POTA will accept it.
There are several possible reasons the why CE3FZL look up did not happen in the field.
As above, it may not be in your selected database.
It may have taken too long to look it up and you began to enter another contact before the DB was finished searching.
Your DB may be able to find the info when your laptop is connected to your home WIFI.
Another possibility is that a call sign might have been entered in error and is not assigned to any amateur radio station. HAMRS will allow the entry, but of course the database cannot find an unassigned call.
In your case CE3FZL is a real station in Santiago, Chile. Congratulations on catching such a rare DX on your first outing!
You might try uploading your ADI with a different browser. As long as all records in your HAMRS log are populated with the required info, the exported ADI should be fine, which suggests a problem on the POTA end.
Feel free to send me your ADIF — would be glad to look at it for you. KZ3L at ARRL.net