Hi @Dothemo and welcome to the forums.
Re : NDIS - I went through a long process but eventually was approved. You can do a 'review of a reviewable decision' and submit further evidence, which needs to be focussed on the functional effects of your 'psychosocial' disability, and also to prove it is 'significant and lifelong'. That's called an internal review and must be viewed and assessed by a 'fresh pair of eyes' and you have to obtain further evidence e.g. psychologist, occupational therapist etc reports - which can cost $$ but it's well worth it if you can do it. (I am using quotes where I've used NDIS language - that alone is hard to understand). If you are knocked back again the NDIS will usually state the parts of the act that you haven't proven adequately. You can then go to the Administrative Appeals Tribunal (AAT) and this time it's called an external review. The AAT can over-rule the NDIS's decisions. I went through this whole process and it was at the AAT review preparation that I got a disability advocate who also got me a legal aid solicitor. It's true, there needs to be something unique about your case to tackle them at this level. In my case it was specifically the interaction of bipolar 1 and complex PTSD and their impact on each other. And the NDIS conceded and accepted me 2 days before the hearing was scheduled.
You can google for disability advocacy in your state e.g. disability advocacy canberra and you will find several organisations that do it - I just had a look.
I started a thread called Anyone started with the NDIS? when I started that process and it has a lot of details peppered through it if you're up to reading it. Page 57/58 in particular there is a long list of the questions NDIS will ask at your planning meeting when you get to that stage. A lot of that can be addressed in your further evidence if possible.
Don't give up! It took a long time for me to have the win, but my plan package has been over $50000 each year (I'm almost finished my 2nd year as I speak) so it was totally worth the fight even tho it was demoralising at times. Having the funds package and having support workers and much more access to psychology (weekly instead of just the 10 per year under the mental health care plan), transport allowance, co-ordinator of supports, financial plan manager ..... and much more community and social access and assistance with daily living.
You are welcome to ask me questions if you want to, either here or on the other thread I mentioned. I know the whole thing is daunting and something of a roller coaster of feelings when you get declined, but worth persevering if you possibly can.
Just @tag me if you want me to respond e.g. @eth so I will get a notification of your post to me. Type @ and you will get a drop-down box with my name in it that you can click on.
Take care and have hope!