1- Start by removing the QWC application as this only links to the existing company file name
2- Proceed to change the QB company file as intended
3- Now go back to BuildTools Accounting page and click on Set up new computer to download a new QWC file
4- Click to open the downloaded file and provide permission when prompted, you will then see the file in Webconnector
You can now continue to run the sync as usual.
Any questions please reach out to Support