If I was 16 in 2019 and claimed as a dependent by my mother but won’t be claimed this year can I file a stimulus rebate credit? I have not lived with her for almost 2yrs.

As a 17 year old it would be highly unusual if you provided over one-half of your own support.  More than likely your grandparents can claim you as their dependent if you have lived in their home for over one-half of the year.

See the requirements for claiming someone as a dependent under the Qualifying Child rules.

To be a Qualifying Child -

1. The child must be your son, daughter, stepchild, foster child, brother, sister, half brother, half sister, stepbrother, stepsister, or a descendant of any of them.
2. The child must be (a) under age 19 at the end of the year, (b) under age 24 at the end of the year and a full-time student or (c) any age and permanently and totally disabled.
3. The child must have lived with you for more than half of the year. Temporary absences while away at college are considered living with you.
4. The child must not have provided more than half of his or her own support for the year.
5. If the child meets the rules to be a qualifying child of more than one person, you must be the person entitled to claim the child as a qualifying child.
6. The child must be a U.S. citizen or U.S., Canada or Mexico resident for some portion of the year.
7. The child must be younger than you unless disabled.

You may be a dependent for your mother or grandparents. Dependency is tricky. If you are not providing more than half or your own support; housing, food, clothing, transportation, etc., then someone else is. At age 17, you could still be someone's Qualifying Child.

Qualifying child

• They're related to you.
• They aren't claimed as a dependent by someone else.
• They're a U.S. citizen, resident alien, national, or a Canadian or Mexican resident.
• They aren’t filing a joint return with their spouse.
• They're under the age of 19 (or 24 for full-time students).
  • No age limit for permanently and totally disabled children.
• They lived with you for more than half the year (exceptions apply).
• They didn't provide more than half of their own support for the year.

If you can be claimed as a dependent by another taxpayer, you must check the box on your own tax return that says you can be claimed, even if you don’t want to be claimed and even if the other person agrees not to claim you. Checking that box will disqualify you from any stimulus credit. If you can be claimed as a dependent by someone else, failing to check that box is tax fraud.

It seems very likely that your grandparents can claim you as a dependent. Review the other answers carefully to be sure of your situation before you break the law.