My dog wont jump on my bed anymore

My dog is about 3 or 4 years old and healthy. She used to jump on my bed at nighttime to sleep but she suddenly refuses to when i ask her to come up. (she seems a little timid and backs away and lays down somewhere else when i ask her if she wants to for reference) Occasionally i wake up at night to see her in the bed even though earlier she absolutely refused to jump.?? She can jump onto the couch perfectly fine when she wants to (and even if i ask her to) but she refuses my bed specifically and only if i’m in the room or awake to see her jump onto my bed 😞😞 Why is this and is there anything i can do?