Good breakdown of the major holdup.
Basically, the EU wants an agreement where neither side can undercut the other on things like worker’s rights, environmental protections, and quality standards, if one side goes up the other has to as well or face sanctions.
Outwardly, the Conservatives say the EU is being unfair to the UK and it forces them to give up their sovereignty. Inwardly, as the video mentions, the Conservatives hate it because if Labour takes government and makes sweeping changes in worker’s rights and environmental protections, like Labour usually does, then the Conservatives won’t be able to repeal them later.