The dashboards are different because there are actually different URL's for those using ProConnect Tax and those using PS/Lacerte.

What confuses a lot of folks is that you, as the accountant, do not own the account your clients use to access Link.  Instead, the Intuit Link account for your client beings to your client and it's the same account they use with all Intuit products.  What your invitation does is to connect your account on Link with your clients' so that you can communicate through this portal Intuit provides as the interface.  For that reason, only your clients can reset their accounts by working with Intuit Support.

Your client should follow the hyperlink embedded in your invitation and use the "forget my password" (or something along that line) link on that login page to reset the password/recover the account.  Recognize that Intuit's instructions are often not intuit(ive).  If they are not able to recover the account after following all the prompts, they should reach out to Intuit Support directly.