Here is the Vega 11 Specs from this website: AMD Radeon RX Vega 11 Specs | TechPowerUp GPU Database
Review from same above website shows games can be played at 2560x1440: AMD Ryzen 5 2400G 3.6 GHz with Vega 11 Graphics Review | TechPowerUp
How is your monitor connected to the motherboard? HDMI, DP, DVI or VGA? If connected with HDMI it is possible the max resolution is 1920x1080. Normally connected with DP (DisplayPort) you should achieve maximum recommended Resolution for your IGP.
What does Windows 10 Settings - "Display" show? Does it show 2560x1440?
Also check Radeon Settings to see if you can change or configure the Resolution to be 2560x1440.
Do you have the latest Monitor Driver for your Monitor installed?