Hello Muriel,
Please check and follow all the steps in this guide first. The fact that you “tried everything” is a bit vague. So check that guide and follow the steps that you haven’t already tried previously. Also, check the Advanced Troubleshooting section on the same page.
If the problem persists please provide your System Files and a WinMTR trace which checks your ISP connection path. You can upload these files on Pastebin and reply here with the Pastebin link using the preformatted text option (</>).
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