"Failed to Fetch Update" error when opening app center on newly installed Juno

Question

I just installed Juno and trying to open the app center and this thing popped out, how to fix it?

Failed to Fetch Update

This may have been caused by external, manually added software repositories or a corrupted sources file.

    E: http://packages.elementary.io/appcenter bionic/main amd64 Packages is not (yet) available (File has unexpected size (34849 != 35207). Mirror sync in progress? [IP: 104.28.4.44 80]
    Hashes of expected file:
     - Filesize:35207 [weak]
     - SHA256:d60095dd675259874ea62c6dc1c64d84dd687bc88e2eff9e675199a32a340e44
     - SHA1:e4891242386e767555495f17f9a413ca3f36a316 [weak]
     - MD5Sum:ed4f8383338719748b96e18b3444933b [weak]
    Release file created at: Thu, 03 Jan 2019 13:31:35 +0000
    )
    E: http://packages.elementary.io/appcenter bionic/main amd64 DEP-11 Metadata is not (yet) available ()
    E: http://packages.elementary.io/appcenter bionic/main DEP-11 64x64 Icons is not (yet) available ()
    E: http://packages.elementary.io/appcenter bionic/main DEP-11 64x64@2 Icons is not (yet) available ()
    E: http://packages.elementary.io/appcenter bionic/main DEP-11 128x128 Icons is not (yet) available ()

Answer 1

I believe you have no network connection. Get a wired connection (Ethernet) and open appcenter, it will be able to fetch updates.

Tip: You may face problem with WiFi. If you do, click on the Installed tab from appcenter and install bcmwl-kernel-source driver by clicking free. Your wifi will be working again.