Screen resolution is very low Fedora 27

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What graphics chipset do you have? Check the output of lspci for lines with VGA or Graphics in them. If the max resolution is 1024x768, that means that the driver isn't available or working for that one.

00:00.0 Host bridge: Intel Corporation 82G33/G31/P35/P31 Express DRAM Controller (rev 0a)
00:01.0 PCI bridge: Intel Corporation 82G33/G31/P35/P31 Express PCI Express Root Port (rev 0a)
00:02.0 VGA compatible controller: Intel Corporation 82G33/G31 Express Integrated Graphics Controller (rev 0a)
00:02.1 Display controller: Intel Corporation 82G33/G31 Express Integrated Graphics Controller (rev 0a)
00:1b.0 Audio device: Intel Corporation NM10/ICH7 Family High Definition Audio Controller (rev 01)
00:1c.0 PCI bridge: Intel Corporation NM10/ICH7 Family PCI Express Port 1 (rev 0

This is what I'm getting when i ran "lspci".

It also depends on the monitor itself. More specifically, the EDID information the monitor sends to the graphics adapter.

monitor-get-edid | monitor-parse-edid can read out that information, but there is a small syntax error you have to fix first on line 735 in /usr/bin/monitor-parse-edid

It's an Intel graphics chip and not a really new one, so it should be fine. What is the output of cat /proc/cmdline? Try not using Wayland. When you click on your name to login, before you enter the password, there is a little gear icon. Click on it and select "Gnome on Xorg", then enter your password to login. See if that helps.