Try removing the registered servers and databases and then re-registering your Pastel as a workstation back to the server.

Run - Regedit. HKLM\software\(wow6432node if running 64bit windows)\Softline\Pastel Partner V11
Delete all of the folders under the V11 key.

HKCU\software\VB and VBA Program Settings\PartnerV11
Delete all the folders in brackets eg (DATA2018) but do not delete the Options folder\key

Open Pastel and register as a workstation, pointing to the server\custom\registration folder. Add the demo company installed on your c drive only and check if it will open. Then add the databases on the server and test. If the local data opens and the server data doesn't, you have network or permission issues.