I had the same issue a few days ago; I was using the Smart ThinQ Sensors HACS integration for many months with our frontload LG Washer and frontload LG Dryer (US4000 models, IRC). Restarted HA and the STQ Sensors app no longer would allow me to log in with my account credentials (not social media, but a username and password). Same issue as others. Kept telling me the credentials were not valid, or that there was an error trying to connect, and that I should check the app on my phone to make sure there were not any new terms of service that needed to be accepted. Checked the phone app, and not only were there no new service or privacy terms, the app could no longer control the appliances (they were present in the app, but were not connecting with the actual physical appliances). So the LG Cloud was clearly malfunctioning..or so I thought. I tried clearing cache on my phone app; force closing it (Android) and restarting the app. Nada. Nothing. Zilch. Started two parallel searches for additional info: 1) Googling to see if there was a customer service phone numb;er for LG (there was and it was horrible....one of the worst CSR experiences I've had in years...more abou that later), and 2) just a search to see what the issue whether others had been having the same issues with not being able to log in to the HACS LG Smart ThingQ integration. And it was then that I discovered there was actually an "official" HA LG SmartThinQ integration, albeit with fewer entities exposed than the HACS one.
To make a really long story short, I've given up on trying to use the SmartThinQ Sensors HACS integration, because it has proven to be too unreliable, and I've spent far too much time trying to get it to stay logged in and connected to my washer and dryer. While there are fewer entities exposed in the HA Official LG Smart ThinQ app, using the PAT (personal access token) that is availalbe from the LG Developer site (note: you need to register separately for that site...but a tip, you can use the same username and password, and LG apparently doesn't care...it just makes things a lot simpler to log in if you need to get a new and different PAT). For me at least, the pain and time and trouble trying to get the older HACS integration to stay connected just wasn't worth my time.
What I really was pissed off about initially with not being able to log into the Android phone app when trying to reconnect was that this also (temporarily) broke the Amazon Alexa integration that I have been using since we bought the appliances. The LG ThinQ Android app (and I presume also the iOS app as well, although I do not use Apple), allows you to set your appliance in Alexa to deliver an announcement when the washing machine and dryer have finished their cycles, and you can set it up in Alexa so that the announcement can be made on any number of Echo or Alexa-compatible devices. We have 8 such devices in our home, and depending on what room we are in, hearing an announcement that "Your LG washer cycle is completed" or similar for the dryer, is very helpful....and it avoided entirely the need to muck around with trying to create an HA automation using a smart plug for both the washer and dryer....which itself can be dangerous given that most 15A-rated consumer smart plugs are not intended to be used with appliances like a washer or dryer that have large electric induction motors, which have in-rush current when initially switched on that can, over time fry the relay in a smart plug, or worse, overheat and cause a fire.
But in any event, yeah, I had the same problem with the Smart ThinQ Sensors HACS integration not working. BTW, about an hour ago, I received a notification in HA that the STQ Sensors HACS app was ready to install an update....maybe this is the fix, but frankly, I've spent way too much time mucking around with these LG appliances, and since the official HA integration seems to be working, that's good enough for me at the moment.