On using antiSMASH for secondary metabolite prediction, it was working well for the first 2 jobs, and thereafter it becomes slow and showing pending status. What may be the reason either server is busy or access is limited?
I assume you are submitting a genome through the online web server. If you look on the left-hand side of the status page there is a box that shows the queue length. I think they recently upgraded their servers to accommodate more simultaneous runs, but I have submitted genomes in the past that were immediately processed and subsequent submissions took an hour or so. I have also submitted more complicated genomes (T. vaginalis) and it took a week to get the results back. You can always install this on a local machine to bypass the queue.
I have also mistakenly grabbed a contig only acceession, meaning that instead of AntiSMASHing the entire genome I only SMASHed on subset of the information. When you make that mistake the results are almost immediately posted (unless you are late in the queue) and often there were no operons predicted from that stretch.