Euro 328 won't turn over

That sounds just like the solenoid plunger moving enough to take the play out of the mechanism but not strongly enough to actually move the solenoid plunger its full stroke. Could be as simple as a bad battery, a bad battery terminal connection, bad contact in the battery disconnect plug, bad solenoid, bad terminal 50 wire connection to the solenoid, etc.. First thing to do is just turn the headlights "on" to see if they are reasonably bright (they should be) or not (would indicate a problem in the primary power system) and/or measure the battery voltage (on the battery cable terminal ends, not the battery posts themselves) both with everything "off" and when trying to engage the starter.

 

Another vote for a bad battery or connection. Do you have a Load Tester for a car battery? They are $40 on Amazon and will work on all vehicle battery’s.
Always check the simplest thing first.

 

Recharge battery, install new charged battery, rotisserie are first three suggestions.

 

Solenoid contacts are dirty. ( it will still move and click)

 

I know I’ve seen these 308 starters on other cars.
Like an MGB.

 

Do confirm when the battery was last replaced, and if the starter has ever been rebuilt.

 

Glad that it turned out to be one of the easier issues to correct -- and thanks for posting your eventual findings. Those aftermarket battery terminals that mechanically "clamp" the wire strands are somewhat less reliable than the stock battery terminals (where the wire strands are cast into it) so do require occasional maintenance. It's never easy to mechanical clamp dissimilar metals together to form an electrical connection and not eventually get some corrosion in the long term.