I have submitted a manuscript in a journal and it has been accepted at 11 December 2018. Till now it is not published. I emailed several times to the chief editor but not get any response for a long time.
You should be able to see the typical time to publication by inspecting some recent manuscripts published in the relevant journal. Information should be displayed showing the following dates: submission, acceptance and publication (see the example displayed in the example in the screenshot attached: the publication dates appear under: "+ Article information"). In this instance, the manuscript was submitted in August, 2016 accepted in October, 2016 and published in November, 2016; the publication year for the journal (not displayed, but the date used in citations) was the subsequent year, 2017 – this manuscript appeared in the January edition of the journal, indicated by issue "Number 1".
The publication date assigned by the journal tends to be out of sync with real time. I do not know the origin of this, but I do recall how happy I was as a child to know that I could fetch my comic from the doormat some days before the date on which it was claimed to have been published.
Inspection of the dates on typical submissions (rather than invited papers) will enable you to determine whether your manuscript is subject to an unusually extensive delay.
You should just relax. :-) There is very little that you can influence about the procedure from now on - they might want to compose a journal issue in a balanced way, which might mean that your paper is published sooner - or later - depending of the size of the pile of accepted and corrected papers, and their topics. Don't worry. :-)
Accepted manuscript will be surely published in a Journal. Once your paper is accepted, you may confirm that it is published. May be because of more number of accepted papers in queue, may be your paper does not come in the heading what they have decided till now, may be in mean while if the journal may be concentrating on conference proceedings etc. may take time. There may be also more reasons. As I could understand, the journal responds and communicate to you only when they are clear in a particular volume, issue and year. Till then your correspondence will be taken care. The only thing can be done is you can correspond to them if it is taking more time and be patience.
If the accepted paper is not published till now in a Journal, may be your paper is in waiting. Contact the editor once gain to know the status. Even the editor is not responding, check the other papers which were in the status online. There is no other alternative except to be patience, your paper will surely be published. The editor will take care of your mail, this is fact.
Please don't be tensed as your article is accepted. Accepted article will be published surely. It may take time, sometimes it takes long time. It seems that they are waiting for particular volume and issue.
"As of 1 January 2019 the journal has been transferred to the new Publisher, Springer Nature. The new website is under construction. For the time being, please refer to this temporary website"
So, they are transferring to new publisher. I think this is the main reason for the situation. Don't worry, as your article is accepted, it will surely be published when everything will be okay and functioning as usual.
Good to hear. Springer nature Publisher (Journal name) not mentioned by you is a good one. Go ahead. Thanks for responding. Your paper surely will be published.