Error using Fona 3G HTTP Commands

I am following this instruction from Adafruit using an Uno with Fona 3G. All commands work fine apart from what I need which is sending HTTP pot and get messages where I get this error:

18:08:16.377 → FONA>
18:08:16.862 → PB DONE
18:09:46.385 → NOTE: in beta! Use small webpages to read!
18:09:46.385 → URL to read (e.g.
18:09:46.385 →
18:09:57.868 → ****
18:09:58.043 → Failed!
18:09:58.043 → FONA>

You are showing outputs from an unknown program. So it is difficult to give you tipps.

I don't know the Fona3G but have some experience with SIM900 and HTTP commands.
Ending a HTTP transfer with SIM900 needs the steps:

"AT+SAPBR =0,1"

before starting a new transfer with "AT+HTTPINIT".

But this is only a rough idea, because I don't know what AT commands you were using.