Not able to transfer call

I am using a Grandstream handytone ata 286 to connect a normal analog phone to asterisk and assign a exten. to that. using this I can able to make a SIP call as well as I make a outgoing call to PSTN number.

the problem is that ,
if there is any call from PSTN then I transfer that call to exten (of analog phone) and if I want to transfer the incmoing call to any other SIP exten. from analog phone extn. which is not possible .
I use blindtransfer using # key . and I am able to transfer internal SIP call from analog phone exten to any other SIP phone. but not able to transfer the incming PSTN call. from analog phone exten. to any other extn.

Please Help.

Thanks in advance

you might work around the problem by using the ATA’s transfer feature, probably by hitting FLASH on the analog phone.

To figure out what is going wrong with Asterisk when you try using the # key, try watching the CLI output and /var/log/asterisk/full.