I, also have been having this issue, now for 2 days. Running Windows 10 Pro 64 bit. I tried to download CCleaner Pro again in an attempt to reinstall. The link that License Key Request from Piriform sent me, also, does not work; I get an error message:
"C:\Users\xxxxxl\AppData\Local\Temp\YqriIMAc.exe.part could not be saved, because the source file could not be read.
Try again later, or contact the server administrator."
I sincerely hope this issue will be resolved promptly!