I have a Multiplus-2 48/3000 and a 3000w generator.
The power limit is set to 10A (~2300W)
It charge perfect, but only at 1300W !?
Why not more?
There are a few other settings and the inverter itself.
Is that the model with a 35-32 on the end? (48/3000/35-32) If so that is the max battery amps. 35x 48v is 1680w.
What is the internal charger set to?
Is weak ac enabled?
Are there other loads on the generator?
How full is the battery?
Multiplus 48/3000/35
Multiplus internal charger, power limit is set to 10A, charge current limit is dynamic, typical 60-160A.
Currently ‘Weak AC’ is enabled, but that makes no difference.
No, there is no other load on the generator - it would effect the generator, not the Multiplus 
I charge the battery, so it varies, for example 40-90%