Finally, i've found a source : Bad cable provided by DELL !!! I've installed the VESA certified cable and all is work. Small difference between "handmade" cable from DELL and VESA certified cable (2-3 mm). So, I cant understand that, ur economy in cables.... No comments.  
Hi, Has bought a new AW2721D, but have a problem to connect it to ASUS GeForce RTX 2070 Super Overclocked 8G EVO (DUAL-RTX2070S-O8G-EVO) via display port. Asus has 3 DP ports, none of them has worked with AW2721D. Connection via HDMI is fine, so only DPs are problematic. Used DDU, unpowered both, unpowered ppu - nothing help. HDMI - signal fine DP - OSD wrote "is going to standby" MB is "MSI MPG Z490 Gaming Carbon WiFi" So pls help me )
AW2721D, connection via RTX 2070 DisplayPort