Too much info here, it's hard to read... :confused:

If the telephone line is plugged directly into VR900, try this http://uk.tp-link.com/faq-735.html on change DSL modulation type step, you can force it to VDSL2. When the DSL light is on solid on...

What is your router's current firmware version? If it's old UI, you can check this http://www.tp-link.com.au/faq-467.html and for new blue UI, it appears to be parental control...

Can you share a screenshot of that error? Is the time zone set correctly?

Make sure your smart plug has the latest firmware. Does it show it can't be reached when you control it locally or remotely? Do you try a factory reset?

There is no open API