Unreached status in a FSM

process (clk, reset)
begin
    if (reset = '1') then
        pr_state <= idle;
    elsif rising_edge(clk) then
        pr_state <= nx_state;
end process;


process (pr_state)
begin
    case pr_state is
        when idle => 
                output_pin <= 'Z';
                nx_state <= request_low;

        when request_low =>
                output_pin <= '0';  -- send '0' to output pin

                reset_counter <= '1'; reset to a counter that waits a fixed amount of time
                if (ready_counter = '1') then   -- while counter not zero
                    nx_state <= request_low;  --  stay in the current state
                else
                    nx_state <= request_high; -- else jump to next state
                end if;

        when request_high =>
                    output_pin <= '1'  -- send '1' to output pin
                    .
                    .
                    .
--         other status
                    .
                    .
                    .
    end case;
end process;