Adding a map service in ArcPad 10.2.1 leads to error " HTTP error 400"

Despite the fact that I have followed the three rules in order to read an map service in Arcpad 10.2.1

   The map service must use the Web Mercator projection.
    You must create a map cache on the server.
    The map cache must include the highest level of detail, Layer 0 (equivalent to the extent of the world).

the Arcpad still fails to read the map service, please have a look at the following screenshot which highlights the issue

What might be the issue here ? Any help is appreciated

Many thanks,

Ahmad