My Toddler Is Suddenly Refusing to Sit on the Potty
“Is it a sign of toilet training issues for my (girl) toddler suddenly refusing to sit on potty? She’s had multiple daily accidents for the last 3 weeks because of it but had no issues before”

I would have liked to know your daughter’s age because it is tricky to answer your question without knowing.
I would first take her to the GP to check she does not have constipation, a bladder infection, or diabetes. Alternatively, consider if something has happened to her recently that may have created an emotional reaction to the potty? Has the refusal to sit on the potty happened as she has started nursery/school? Have you recently moved homes, gone through a divorce, or had a new baby?
It is also useful to remember that learning to use the potty is a skill and like with any other skill, learning is not linear, it usually has setbacks. It is not usual for children to experience potty training regressions. So, try to be patient and understanding. Give her gentle reminders about using the potty regularly. When she uses it, praise her and clearly show how pleased you are. Children like their parents to be pleased with them, so they are likely to repeat behaviours their parents like. Do not make a big fuss when she has accidents. Gently tell her that next time she must remember to use the potty. And you should remember that she is not doing it on purpose.
You will find these articles useful:
My 6-Year-Old Is Having a Lot of Accidents
What to Do with Potty Training Regression?
How Many Potty Training Accidents Are Normal?
I hope this helps! I wish you and your daughter all the very best.
Love,
Ana