@cyammine - Your issue seems to be different from the original poster who was selectively trying to capture forms via GTM. As yours is not capturing at all, I would recommend you create a new post with your issue as opposed to posting in one marked as answered so that all members of the community can help out and offer advice as most will not respond to new replies in an answered thread. Also I would recommend you post a link to the page in question as the only way to troubleshoot this initially would be to inspect the page for any runtime errors that may be occuring.
However, if the tag is not firing at all, I would likely recommend in this instance to utilize the testing mode of GTM to see if the tag is indeed firing and if it is not that tool would be the best to determine which code is not firing and it should provide the answers or some insights as to why.