Navigate to location where sqlcesa35.dll is located. You will find a web.config located in that directory. In web.config add the line
<handlers accessPolicy="Read, Execute, Script" /> line after <directoryBrowse enabled="false" />
<?xml version="1.0" encoding="UTF-8"?>
<configuration>
<system.webServer>
<directoryBrowse enabled="false" />
<handlers accessPolicy="Read, Execute, Script" />
</system.webServer>
</configuration>
Save and restart the website.
This worked for me. It was downloading the .dll file rather than executing it