I had a similar issue on my CicviCRM fresh installation (CiviCRM 5.10.4) -> IIS10 webserver.

Error used to happen on both Joomla (3.9.3) and WordPress (5.0.1) versions.

The problem was that we see any relationship or activities table (DataTables warning: table id=DataTables_Table_0)

So, what I did to fix this problem is to add the following values in the app web.config. Do not forget any of these or it won't work.

<system.web>
    <httpRuntime maxQueryStringLength = "12288" maxUrlLength="12288" />
</system.web>
<system.webServer>
    <security>
        <requestFiltering allowDoubleEscaping="false">
            <requestLimits maxAllowedContentLength="3000000000" maxUrl="4000000" maxQueryString="4000000" />
        </requestFiltering>
    </security>

    <httpErrors existingResponse="PassThrough"></httpErrors>
</system.webServer>

Hope this helps !

I had a similar issue on my CiviCRM fresh installation (CiviCRM 5.10.4) -> IIS10 webserver.

Error used to happen on both Joomla (3.9.3) and WordPress (5.0.1) versions.

The problem was that we see any relationship or activities table (DataTables warning: table id=DataTables_Table_0)

So, what I did to fix this problem is to add the following values in the app web.config. Do not forget any of these or it won't work.

<system.web>
    <httpRuntime maxQueryStringLength = "12288" maxUrlLength="12288" />
</system.web>
<system.webServer>
    <security>
        <requestFiltering allowDoubleEscaping="false">
            <requestLimits maxAllowedContentLength="3000000000" maxUrl="4000000" maxQueryString="4000000" />
        </requestFiltering>
    </security>

    <httpErrors existingResponse="PassThrough"></httpErrors>
</system.webServer>

Hope this helps !