I am using a mid 2015 MacBook Pro running HighSierra v 10.13.2 and just upgraded to Plex media server v. 1.10.1.4602 today. the problem existed before the upgrade but appears to be significantly worse after the upgrade. I use an Amazon Fire TV Stick running Plex version 6.12.0.3239.
When I choose media to play on the plexapp on fire tv stick, the show will load and I may get a second or two or perhaps a larger portion of a minute before it will stall for a minute or so before the gray box with the error message “Connection to server isn’t fast enough…” will appear. If I go onscreen to the settings cog and change the transcoding settings to something lower, it may restart for a moment but again I will not achieve a full minute before I get the same error. There is no transcoding setting available that will work, the lowest being 0.3. In the past, a month or so ago, I was able to overcome this problem when it would rarely occur by selecting a lower bitrate (transcoding setting) and suffer a lower quality of video in order to have continual video however there is no tradeoff now available. Log files are attached.
In my humble opinion it’s your Fire stick and Wifi connection.
For best results to a TV use Gigabit Ethernet router with Cat 6 or Gigabit powerline adapters for connection to a TV player like a Roku device. I could go into all the things that can go wrong with Wifi but it will always be troublesome in some environments with High bit-rate Video.
Have you got your Mac connected to the Internet/WAN with Ethernet and use a Wifi Router/modem?
I’m finding the error message of Network connection not fast enough “Bogus” at best. With an internal network Bandwidth of 180 Mbps and Plex dashboard showing 18-20 Mbps for streaming. Plex needs to correct the errors forthe server section to reflect the true cause of the connection issue. I run wi-fi service to my Apple TV and IOS devices. In troubleshooting the Bandwith issue I ran an ethernet cable to my Apple TV. At first the issue seemed to fix the issue but several days later the bandwidth issue arose again with an ethernet cable. This leads me to believe the notification is something else. Plex Please address network connection issue and resolve it.