Toddler holding on to wee during potty training and seems to be in pain

[gagama]

My daughter is with me with her nearly 3-year old daughter. They are toilet training her but she seems to be holding on to her wee and is in pain. What can we do?

My granddaughter is nearly 4 and is the same, she refuses to use the toilet or potty and will wait hours and hours until she gets a nappy.
When asked she just says she doesn't like the toilet or the potty.
Her father died quite suddenly last year as they had started the training but due to the issues following the death a lot of stuff such as set bedtimes, potty training etc went out the window.

So any help or advice would also be appreciated