I know in AEM if language copy was already created, it considers it update language copy while trying to translate it again. Is there a way I can send a content for translation again while there is no changes in the content?
Right now it gives error as below if I try that:
No translation project created, There is no change detected between /content/experience-fragments/app/en/xyz /content/experience-fragments/app/fr/xyz
I have a Job that resend failed translations back to vendor and for that I need to restart jobs by sending my pages/experience fragments back to Translation projects. Since a language copy was already created when I sent the translation for the first time, now when I retry those translations it says there is no change in the content.
By the term "failed translations" you mean the translation Job Status or incorrect translated content with status being "Ready for Review or Approved"
Your observation on log message is per the OOB implementation - Update Language copy action won't create a Translation project itself for already existing language copy when there is no change in the source copy.
You can create a new Translation project (Projects > Create > Translation Project) and while adding the desired page to the job it is possible to update the language copy: