I submit and share this as I passed trough sour moments trying to restore Laserfiche to an operational state after the name change. Such an easy thing to do but it is not very clear what has to be done to get LF up and running again, so I hope this can help others.
At a customer's LF installation, the Systems manager decided to change the LF host server name. The OS is Windows Server 2012R2, and he did this with the Server Manager utility in Windows Server. So far so good he tought, easy trick, but of course Laserfiche was totally unoperative after that. That is when he called for support.
The case was solved eventually, and first thing this case taught me is that if you can avoid changing the name of a server, then please avoid it, haha. But if you must, or like in this case, someone else did, then this is what, at the end, worked:
Getting Laserfiche server to reconnect to the server and re- register the repository is the easy part. It can be done in minutes in the LF console and windows client and get it working again is easy. The web apps, that´s a little trickier, specially Web Access and the App Server that takes care of the mobile access.
For Web Access, uninstalling and reinstalling URL Rewrite Module, and manually adding repository and changing server name to the new name in the xml file (c:\Program Files\Laserfiche\Web Access\Web Files\Config\WebAccessConfig.xml - restart IIS) worked.
For Mobile, (App Server) manually changed the server name in the xml config file. (c:\Program Files\Laserfiche\Mobile\Web Files\Config, after that, restart IIS)