My Sharp UX-A255 won't let me fax anything. It

Is it receiving faxes? Make sure you have the line in the right place in the back of the machine (line) and that you get dial tone (hit the monitor button if it has one). Try calling it on your cell to see if it picks up. You may have a poor phone line conditon, and you could try to slow the modem speed down or check the ECM (Error Correction Mode) if so. If it's a jamming problem, try to run a copy and see if it feeds ok. If not try cleaning the feed/pick up rollers with mild soap and water. Reseat the paper and try it again.