For security purposes, Windows Update is complying with Security Advisory 2868725, which recommends removing support for RC4. Therefore, Windows Update has discontinued support for the RC4 cipher. If your computer is configured to use only cipher suites that are not supported by Windows Update (such as those that include RC4), this will prevent the computer from obtaining updates through Windows Update.
Alternative ciphers, such as AES, will continue to work. For more information about cipher suites and about which ciphers are supported in Windows, see Cipher suites in TLS/SSL (Schannel SSP).
To mitigate this issue, enable cipher suites that use alternative ciphers that are supported by Windows Update, such as AES.