cannot execute DELETE in a read-only transaction

Hi, I'm trying to delete an entry through a database function when the user calls this function, but I always get this error.

I already checked

select pg_is_in_recovery();

select pg_is_in_recovery();

and

show default_transaction_read_only;

show default_transaction_read_only;

.
I also tried to set

set transaction read write;

set transaction read write;

but then I'll get this error:

set transaction read write;

set transaction read write;

.

Please help