As it says - missing VSS system writer. A Windows issue

Check with "vssadmin list writers" - the system writer will be missing.

You will find a bunch of repair utilities on the internet. Be careful as they are OS dependant.

Place save -a '"ignore-all-missing-system-files=yes"' into backup command.

Please find writer list and we're using windows server 2008 R2.  Enterprise sp1

Networker version : 7.6

vssadmin 1.1 - Volume Shadow Copy Service administrative command-line

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Writer name: 'Task Scheduler Writer'

   Writer Id: {d61d61c8-d73a-4eee-8cdd-f6f9786b7124}

   Writer Instance Id: {1bddd48e-5052-49db-9b07-b96f96727e6b}

   State: [1] Stable

   Last error: No error

Writer name: 'VSS Metadata Store Writer'

   Writer Id: {75dfb225-e2e4-4d39-9ac9-ffaff65ddf06}

   Writer Instance Id: {088e7a7d-09a8-4cc6-a609-ad90e75ddc93}

   State: [1] Stable

   Last error: No error

Writer name: 'Performance Counters Writer'

   Writer Id: {0bada1de-01a9-4625-8278-69e735f39dd2}

   Writer Instance Id: {f0086dda-9efc-47c5-8eb6-a944c3d09381}

   State: [1] Stable

   Last error: No error

Writer name: 'ASR Writer'

   Writer Id: {be000cbe-11fe-4426-9c58-531aa6355fc4}

   Writer Instance Id: {99150269-9d2b-4630-8f32-3e93c99531c0}

   State: [1] Stable

   Last error: No error

Writer name: 'System Writer'

   Writer Id: {e8132975-6f93-4464-a53e-1050253ae220}

   Writer Instance Id: {94a32fd9-6357-4c83-9d94-e788b2be222b}

   State: [1] Stable

   Last error: No error

Writer name: 'SqlServerWriter'

   Writer Id: {a65faa63-5ea8-4ebc-9dbd-a0c4db26912a}

   Writer Instance Id: {f37c80d9-1637-4ee9-8af1-4e9ca324735e}

   State: [1] Stable

   Last error: No error

Writer name: 'FSRM Writer'

   Writer Id: {12ce4370-5bb7-4c58-a76a-e5d5097e3674}

   Writer Instance Id: {332eea35-6370-4206-b590-82cd37485c66}

   State: [1] Stable

   Last error: No error

Writer name: 'Shadow Copy Optimization Writer'

   Writer Id: {4dc3bdd4-ab48-4d07-adb0-3bee2926fd7f}

   Writer Instance Id: {461b65a8-6bd9-44ee-87cf-778365bbd9fa}

   State: [1] Stable

   Last error: No error

Writer name: 'COM+ REGDB Writer'

   Writer Id: {542da469-d3e1-473c-9f4f-7847f01fc64f}

   Writer Instance Id: {fd214401-4ec0-4f6e-849b-1c29b1ec043a}

   State: [1] Stable

   Last error: No error

Writer name: 'Registry Writer'

   Writer Id: {afbab4a2-367d-4d15-a586-71dbb18f8485}

   Writer Instance Id: {a65838d5-da07-436c-a95b-dc9d14e01c71}

   State: [1] Stable

   Last error: No error

Writer name: 'WMI Writer'

   Writer Id: {a6ad56c2-b509-4e6c-bb19-49d8f43532f0}

   Writer Instance Id: {6a543138-8884-44a4-a553-0040103d8c6a}

   State: [1] Stable

   Last error: No error

7.6?  I would dump that and use 8.1.2.x at least.

You must check/repair the client, not the NW server.