Reading and writing Tags

I have two PLC's connected. On one I can create new tags and read and write from them. On the other i can read and write from older tags, but i cannot read or write from any new ones that I create. This also applies if I modify an old one. any Ideas?

For ideas i only have two kind of obvious but are the first thing i check.

That you've created in the PLC? If so, i would take a look if they're accessible or if there are any diferences in the configuration compared to the old ones.
I would also make sure the path to the new tag is correct, if they're in the same DB or UDT, maybe even datatype.
What errors are you getting when you try to read the tags? What are the quality codes on these new tags? Are the PLCs the same model?

Good Afternoon:

I am not getting any errors. They work within Ignition, but they do not seem to be able to reach the PLC. Other tags to the same PLC that were created earlier all work. If I modify the address of an existing tag it will not work.

Hope this helps.

Make sure the new tags you create are in the same scope as the old tags. I've accidentally created program-scoped tags instead of controller-scoped tags many times.

If you are using Ignition's logix driver, did you turn off automatic PLC rebrowse?