On arrival visa at Muscat Airport

Two conditions must be fulfilled if you are planning to acquire GCC on-arrival in Muscat (and other GCC countries -- except UAE):

1- You must have your original Saudi Iqama along with you.
2- You must have traveled from one of the GCC country.

I had experience with #2 recently in Muscat. I didn't travel from GCC to Muscat expecting that I'll get the on-arrival based on my Saudi iqama. They initially refused. I was with kids and had to negotiate with their immigration officer for some 15 minutes. They finally gave it to me with an advice not to do that again.

Thanks..you means that you travelled from country other than GCC, for example from Jordan. Had you traveled from Dubai, you would have not  faced problem.
I am correct?

Yes, your understanding is correct.