What date are you trying to make a reservation for? Reservations for Polish trains can be made 30 days in advance. 

Trains TO PL-and I guess-why not state more clearly??-from DE; these canNOT be RES online-has to do in person at a DB or other station that is connected to that system-extra cost 6€. OR do it in the real old-style IR spirit and use local trains-just look further as that first option-in the past printed timetable books were quite good for taht-these new planners make people dumb.anna fra Sverige-above-always gives links to the ALT site by seewulf on howtodo RES by yourslef and also save money that way

LOcal trains IN PL-the IC etc by PKP-from 30 day advance and best yourself at a counter-for free.