Hello @certifledtank, welcome to the forums.
We are not affiliated with the R6 stat tracker website so we are unable to comment on its accuracy, but our official R6 stat website can be found here > https://www.ubisoft.com/en-us/game/rainbow-six/siege/stats/
Sometimes MMR/renown received at the end of a match will not show, as the scoreboard may not sync to our server in time, but usually, your MMR/renown will be added to your account by the time 24 hours have passed.
If after 24 hours have passed and you do not believe you have gained any MMR for that match, please let us know the exact time and date of the match and get in touch with us via our website > https://www.ubisoft.com/help/contact
Please note, whilst we can check this for you to make sure this is not a bug, we are unable to add any MMR or adjust this, but we can pass this on to our Siege team to make them aware of any MMR and data sync issues that might be affecting players.