@LDSenpai,

If you have that warning that the router is unable to connect to our cloud servers, you will not be able to do any of the automatic updates. You will only be able to use the firmware files from our site. Double-check that you have the correct hardware version by looking at the label on the bottom of the router, some interfaces will report that you have version 3 even though you really have version 3.6

What were the slow speeds like on the router? This may be the issue that is preventing the cloud service connection.

If you connect directly to the modem, are the speeds what you would expect?

The most straightforward solution would be to reset the router to see if there was a setting that was affecting the connection. If you are presented with the option to sign in with your TP-Link ID, I would highly recommend this, as this would most likely require that your router connects to the same servers as the firmware updates would.