SPA509G - Failed to acquire SLA slot for DN "ext"

[mrh0n]

I have followed the administrative guide for my phone and browsed the web for any related topics but I can not seem to find anything with a good answer.

My 3cx log says "Failed to acquire SLA slot for DN "ext"" when I try to call from an Aastra to my SPA509g

Thanks guys for any help.