Look at the folloing diagram (Fig-1) and know the answer to your question:
Figure-1:
In Fig-1, pb5 is configured as input line. Now, Rip resistor is in series with Led circuit with 5V excitation. The Led current is too small (5000-2500/(1000+20000) ~= 0.12 mA) compare to 10 mA to get good light from the Led.