I never notice what is its cause.
I've done tag check, and all tags are inserted properly.
Any input is welcomed.
Can you send the original source file and the TM to the support e-mail address?
Did you set the Translated status before saving the file?
Yes, the recent CT version.
I didn't notice any padlock...
This file was pre-translated in Studio by the client.
I tried again (insert exact matches) in CT, using the newly downloaded source SDLXLIFF.
But it still does not work.
So I had to apply exact matches in Studio.