Check with spare PC, this will ruleout ISP and steam in other end and problem is at your end.

ps.
then other crazy ideas like full drives or wrong steam default drive is full in steam settings and antivirus app block it, or check disk at system OS tool is need to check drives.

if wifi, try use cable, just incase you have alot of bad packets or bad signal that cancause issue, it cant be that if otyher online client is working.

So many what if this and that here.

even change steam DL zone, its still Black friday, and ppl still load many games down next 2-3 days after event, even that is possible.

most network issue goes away when event is over thats just only confirm traffic into a steam server is the issue, and pressure on lines though all them ISP is reduce.

Most ppl know this, ente a store on black friday, no service ia avalable asap, this is smae on internet but there is no cue line atm at internet, i just poijt it out it could be this.

Also why have a internet issue doing a steam event sale is bad, most will not use 2 sec on it to try solve it.

ISP do not build fiber for a sale event thats over in a flash, temoprary incresed network congested area will not be fixed, but ISP can learn from them and reoute other traffic on diffrent lines, if they even do this. require you talk with own ISP, if they even have such choise.

I did say talk with them, not argue with them. ( all ISP in the world should try have our lines in gameserver with a better service if they even can that, this will not go away. )

Understand why i said it.

we are steam users here we have no power what is going on from your wallplug though ISP and there partners partner into steam and back from them.

So what they are doing and how matters, sometimes they try there best and other times it look like fiber lines or knowledge about game DL server is put together by worst kind of humans with no insights. ( so yes ISP traffic mangement and understand who things work from a gamers view point matetr ) it is not orinary traffic, its should have management in why we do this., im not so sure ISP think we specific users with a DL needa, for them it could just be traffic, vut we dotn DL all the time this is the complex part many forget here.

And that why i bother dare or try explan it, ( this is for all steam usre no just you, as i said many ISP might know this but then you look at partners partner, you only need 1 ro ruin it for the many in all out diffrent fiber lines into a steam server.

also why we all feel we are alone when it work for all others. ( and sometime it is our own pc only ) this is the triggy part.