Hi @Daniel M ,
To narrow down this issue, let's verify the followings:
- Did you install patches on your SharePoint farm recently? If yes, have you installed patches on all your APP servers and WFE servers? And have you also installed MUI/language patch if there is? Have you run SharePoint 2016 Products Configuration Wizard or executed
PSConfig.exe -cmd upgrade -inplace b2b -force -cmd applicationcontent -install -cmd installfeatures
after installing patches on all SharePoint servers in your farm?
There is an article about troubleshooting such issue for your reference: SharePoint 2016 Product / Patch installation or server upgrade required.
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