Nodes not all appearing in the node-red

I am new in node red and I have installed node-red-contrib-iiot-opcua but but only few nodes appear in the node-red which are opcua iiot Lister, Opcua IIoT Write and OPCUA IIoT Discovery. this means that 3 out of 18 nodes appear. if anyone can help, I will appreciate it
thank you

When you start Node-RED, what version of Node-RED and nodejs does it say you are using?

Also check to see if there are any error messages

thanks ukmoose for replying. when I start Node-red it show that the version is v0.20.7 with node.js being v10.16.0.

There is no error that is displaying when i start the Node-red in the raspberry pi 3 terminal. i have tried to solve this by unistalling and installing the nodes in the manage palette but still nothing seems to change as the nodes in the manage palette appearing in grey square and unusable.

If theres no error, you should open up an issue on the nodes github page to contact the author.

If you import the examples as described in the readme then does it show some of the nodes not available?

Thank you Colin the reply.
When I try to import the examples, Node-red pop-ups small screens that says these I have imported the unrecognized nodes and its list them in bullet form. and in flow these nodes appear like " unkown: OPCUA-IIoT-Inject", "unkown: OPCUA-IIoT-Server"

Unknown not unkown, sorry for that

Go to your .node-red directory and run
npm install node-red-contrib-iiot-opcua
Post here what it says.

this what it show after doing whta you told me to do Colin. Its the same thing that I have been getting when I try to install this opcua nodes.

Nothing obvious wrong, you will have to ask via an issue on the node's github page as suggested by @ukmoose earlier.

okay Colin I will do that, thank you for your help