this particular issue is caused by using a map that doesn't have enough flat terrain available for bases to spawn on.
potential solutions... you could experiment by allowing water spawns by enabling them in the Water Settings of each profile
"Water Settings": {
"Allow Bases To Float Above Water": true,
"Chance For Underwater Bases To Spawn (0-100) (BETA - WORK IN PROGRESS)": 0.0,
"Spawn On The Surface Of Water": false,
"Ignore Land Level On Seabed": false,
"Prevent Bases From Floating Above Water By Also Checking Surrounding Area": false,
"Maximum Water Depth Level Used For Float Above Water Option": 1.0,
"Minimum Water Depth Level Used For Seabed Option": -20.0,
"Maximum Water Depth Level Used For Seabed Option": -35.0,
"Torpedo Damage Multiplier (Min)": 3.0,
"Torpedo Damage Multiplier (Max)": 3.0
},
a more thorough approach is to force the spawns on the water surface (since there is not enough terrain to use elsewhere)
"Water Settings": {
"Allow Bases To Float Above Water": true,
"Chance For Underwater Bases To Spawn (0-100) (BETA - WORK IN PROGRESS)": 100.0,
"Spawn On The Surface Of Water": true,
"Ignore Land Level On Seabed": true,
"Prevent Bases From Floating Above Water By Also Checking Surrounding Area": false,
"Maximum Water Depth Level Used For Float Above Water Option": 1.0,
"Minimum Water Depth Level Used For Seabed Option": -20.0,
"Maximum Water Depth Level Used For Seabed Option": -35.0,
"Torpedo Damage Multiplier (Min)": 3.0,
"Torpedo Damage Multiplier (Max)": 3.0
},
lastly,
you could use the Spawns Database plugin to use Spawns Database File in your profile. just make sure the spawn point can hold a base of relative size. if it doesn't spawn then enable Ignore Safe Checks. enable Prevent Building Until Base Spawns as well to prevent players from overtaking the area. this will force the plugin to use a specific spawn point, which if configured will ignore safe checks.