What I can see when I follow the debug messages is that ESP needs STA mode and calls up AP-STA Mode while Blynk will bring the ESP in AP Mode where ESP does not work.
Actually Blynk should also work in APSTA but not sure where I can change the WIFI-Mode Settings.
For now I used a workaround and transfer the data two a second ESP per UART and send it from there then to Blynk.