Is it normal for parents to invalidate mental disorders?

Parents invalidating their children's mental health problems is common, but not normal. Perhaps they're in denial?

I experience my mom fluctuating between saying i'm making excuses and saying that I need to accept some things are harder for me and there's nothing wrong with that. Either or can be frustrating for different reasons.
Most important thing is that you know what you are capable of and not and that you accept yourself. People around you, including your parents, can never know what it's like unless they happen to have the exact same struggles which is unlikely as not even everyone with the same mental health problems experience the same symptoms or copes with them the same way.
Not being able to work is frustrating. People will always use the "its an excuse to get out of work" but it sucks living on disability checks, your economy is very limited and you can't do much not to mention it gets boring not having the routine of a job to go to everyday.
If you're an adult you can simply ignore your parents, talk to friends instead or a therapist when it comes to your struggles. If they are willing to at least listen, wether they will understand or not, you can try to talk to them about how these things affect you and maybe send them some links or refer them to discussion groups and forums for people with these problems.

Unfortunately, sometimes parents can't understand or don't want to acknowledge when their child has mental problems. Coming from a similar scenario, I understand what you're going through and can give at least a bit of advice. Sit down with them, and have a talk about how your problems make life more difficult for you and why. If that doesn't help, you could always invite them to an appointment with your PCP and have them explain to your parents how the things you are experiencing are real.

There are two very common problems here:

1) Mental Health "experts" often misdiagnose mental conditions and apply labels that don't actually apply.

2) Parents often suppress negative information about a friend of family member and ignore that it could be affecting a person.

If a parent ignores a false diagnosis they do no harm - and often do a lot of good.

IF they ignore a real diagnosis they often do harm; but may do a lot of good by encouraging their child to overcome "whatever" it is. Read about Napoleon Hills "death" (no hearing) son's successful life (Think & Grow Rich).

If a Mental Health Professional incorrectly diagnoses a condition - they usually do a lot of harm.

This is gonna sound really mean but its because in the real world the "excuses" dont change your outcome. No one cares about why the guy is working at McDonalds because no matter why he still works at McDonalds. I didnt write the rules but thats the way it is. They probably see minimum wage in your future and they arent gonna accept that for you so they're gonna force you to try 10x harder to keep up with the others.

I'm sorry, I have to point out the irony in them not believing you when they're the ones who helped you accept you have these disorders

It may be possible they see something in you they think will be self-destructive, though

I suggest being alone for a bit and really think about things. Be honest with yourself, identify every feeling you have and consider their existence