Negotiation details are intentionally kept private about what concessions and what was tentatively agreed to.

Here's a video from the Saturday morning Aug 22 press conference from Mark Carney the day after the negotiations were suspended:

https://www.cpac.ca/headline-politics/episode/pm-carney-speaks-to-media-after-suspension-of-canada-us-trade-talks?id=6b77d2c2-d09d-47fb-9bf1-7c88f3c2445c

At @23:07 he was asked What specific last minute changes made the deal untenable? Paraphrasing his response was:

• level and scope of the tariffs for the auto industry with no tariff rollback for medium and heavy duty trucks
• veto over Canada’s ability to make trade deals with other nations
• restrict protections on language and culture