If you flashed a used ESP, sometimes the esp module does not want to connect to wifi. In the config portal it seems to connect and the blue led blinks 3 times but it still didn't connect. The ESP is not saving the credentials, this is because there is already a filesystem on the ESP with a different format. In general, if you cleanup the memory of your ESP (e.g. flash something on it with the option "erase flash and wifi settings", ( see the picture below ) and then reflash the ESP-ECU binary, it will work.

Another trick: Watch the serial monitor while connecting and if you see "Youpy, connected!" push the resetbutton. The Esp wil now reboot and connect, showing its IP.

If not, as a workaround, you can first flash another program, (with Flash Size configuration 4MB(FS:2MB OTA:~1019KB)) for example a basic web server, with the wifi credentials hardcoded. If this connects, you can flash the ESP-p1meter. This will then connect with the already existing credentials. The admin password now is probably 0000. You can change this by starting the AP via the menu.